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<button class="button is-small is-link">Go</button> </div> </div> </form> </div> </div> <ol class="breathe-horizontal" start="1"> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2502.19490">arXiv:2502.19490</a> <span> [<a href="https://arxiv.org/pdf/2502.19490">pdf</a>, <a href="https://arxiv.org/format/2502.19490">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Strongly Correlated Electrons">cond-mat.str-el</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> </div> <p class="title is-5 mathjax"> Signatures of collective photon emission and ferroelectric ordering of excitons near their Mott insulating state in a WSe$_2$/WS$_2$ heterobilayer </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Devenica%2C+L+M">Luka Matej Devenica</a>, <a href="/search/cond-mat?searchtype=author&query=Hadjri%2C+Z">Zach Hadjri</a>, <a href="/search/cond-mat?searchtype=author&query=Kumlin%2C+J">Jan Kumlin</a>, <a href="/search/cond-mat?searchtype=author&query=Li%2C+R">Runtong Li</a>, <a href="/search/cond-mat?searchtype=author&query=Li%2C+W">Weijie Li</a>, <a href="/search/cond-mat?searchtype=author&query=Forrero%2C+D+S">Daniel Suarez Forrero</a>, <a href="/search/cond-mat?searchtype=author&query=Vento%2C+V">Valeria Vento</a>, <a href="/search/cond-mat?searchtype=author&query=Ubrig%2C+N">Nicolas Ubrig</a>, <a href="/search/cond-mat?searchtype=author&query=Liu%2C+S">Song Liu</a>, <a href="/search/cond-mat?searchtype=author&query=Hone%2C+J">James Hone</a>, <a href="/search/cond-mat?searchtype=author&query=Watanabe%2C+K">Kenji Watanabe</a>, <a href="/search/cond-mat?searchtype=author&query=Taniguchi%2C+T">Takashi Taniguchi</a>, <a href="/search/cond-mat?searchtype=author&query=Pohl%2C+T">Thomas Pohl</a>, <a href="/search/cond-mat?searchtype=author&query=Srivastava%2C+A">Ajit Srivastava</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2502.19490v1-abstract-short" style="display: inline;"> Spontaneous symmetry breaking, arising from the competition of interactions and quantum fluctuations, is fundamental to understanding ordered electronic phases. Although electrically neutral, optical excitations like excitons can interact through their dipole moment, raising the possibility of optically active ordered phases. The effects of spontaneous ordering on optical properties remain largely… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2502.19490v1-abstract-full').style.display = 'inline'; document.getElementById('2502.19490v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2502.19490v1-abstract-full" style="display: none;"> Spontaneous symmetry breaking, arising from the competition of interactions and quantum fluctuations, is fundamental to understanding ordered electronic phases. Although electrically neutral, optical excitations like excitons can interact through their dipole moment, raising the possibility of optically active ordered phases. The effects of spontaneous ordering on optical properties remain largely unexplored. Recent observations of the excitonic Mott insulating state in semiconducting moir茅 crystals make them promising for addressing this question. Here, we present evidence for an in-plane ferroelectric phase of dipolar moir茅 excitons driven by strong exciton-exciton interactions. We discover a surprising speed-up of photon emission at late times and low densities in excitonic decay. This counterintuitive behavior is attributed to collective radiance, linked to the transition between disordered and symmetry-broken ferroelectric phases of moir茅 excitons. Our findings provide first evidence for strong dipolar inter-site interactions in moir茅 lattices, demonstrate collective photon emission as a probe for moir茅 quantum materials, and pave the way for exploring cooperative optical phenomena in strongly correlated systems. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2502.19490v1-abstract-full').style.display = 'none'; document.getElementById('2502.19490v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 26 February, 2025; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2025. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2410.17930">arXiv:2410.17930</a> <span> [<a href="https://arxiv.org/pdf/2410.17930">pdf</a>, <a href="https://arxiv.org/format/2410.17930">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Disordered Systems and Neural Networks">cond-mat.dis-nn</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Materials Science">cond-mat.mtrl-sci</span> </div> </div> <p class="title is-5 mathjax"> Positive oscillating magnetoresistance in a van der Waals antiferromagnetic semiconductor </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Lin%2C+X">Xiaohanwen Lin</a>, <a href="/search/cond-mat?searchtype=author&query=WU%2C+F">Fan WU</a>, <a href="/search/cond-mat?searchtype=author&query=Ubrig%2C+N">Nicolas Ubrig</a>, <a href="/search/cond-mat?searchtype=author&query=Liao%2C+M">Menghan Liao</a>, <a href="/search/cond-mat?searchtype=author&query=Yao%2C+F">Fengrui Yao</a>, <a href="/search/cond-mat?searchtype=author&query=Guti%C3%A9rrez-Lezama%2C+I">Ignacio Guti茅rrez-Lezama</a>, <a href="/search/cond-mat?searchtype=author&query=Morpurgo%2C+A+F">Alberto F. Morpurgo</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2410.17930v1-abstract-short" style="display: inline;"> In all van der Waals layered antiferromagnetic semiconductors investigated so far a negative magnetoresistance has been observed in vertical transport measurements, with characteristic trends that do not depend on applied bias. Here we report vertical transport measurements on layered antiferromagnetic semiconductor CrPS$_4$ that exhibit a drastically different behavior, namely a strongly bias dep… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2410.17930v1-abstract-full').style.display = 'inline'; document.getElementById('2410.17930v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2410.17930v1-abstract-full" style="display: none;"> In all van der Waals layered antiferromagnetic semiconductors investigated so far a negative magnetoresistance has been observed in vertical transport measurements, with characteristic trends that do not depend on applied bias. Here we report vertical transport measurements on layered antiferromagnetic semiconductor CrPS$_4$ that exhibit a drastically different behavior, namely a strongly bias dependent, positive magnetoresistance that is accompanied by pronounced oscillations for devices whose thickness is smaller than 10 nm. We establish that this unexpected behavior originates from transport being space-charge limited, and not injection limited as for layered antiferromagetic semiconductors studid earlier. Our analysis indicates that the positive magnetoresistance and the oscillations only occur when electrons are injected into in-gap defect states, whereas when electrons are injected into the conduction band the magnetoresistance vanishes. We propose a microscopic explanation for the observed phenomena that combines concepts typical of transport through disordered semiconductors with known properties of the CrPS$_4$ magnetic state, which captures all basic experimental observations. Our results illustrate the need to understand in detail the nature of transport through vdW magnets, to extract information about the nature of the order magnetic states and its microscopic properties. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2410.17930v1-abstract-full').style.display = 'none'; document.getElementById('2410.17930v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 23 October, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">10pages, 7 figures, under evaluation</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2405.17144">arXiv:2405.17144</a> <span> [<a href="https://arxiv.org/pdf/2405.17144">pdf</a>, <a href="https://arxiv.org/format/2405.17144">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Materials Science">cond-mat.mtrl-sci</span> </div> </div> <p class="title is-5 mathjax"> Brightened Optical Transition as Indicator of Multiferroicity in a Layered Antiferromagnet </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Multian%2C+V">Volodymyr Multian</a>, <a href="/search/cond-mat?searchtype=author&query=Wu%2C+F">Fan Wu</a>, <a href="/search/cond-mat?searchtype=author&query=van+der+Marel%2C+D">Dirk van der Marel</a>, <a href="/search/cond-mat?searchtype=author&query=Ubrig%2C+N">Nicolas Ubrig</a>, <a href="/search/cond-mat?searchtype=author&query=Teyssier%2C+J">J茅r茅mie Teyssier</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2405.17144v1-abstract-short" style="display: inline;"> Two-dimensional van der Waals magnets show strong interconnection between their electrical, magnetic, and structural properties. Here we reveal the emergence of a luminescent transition upon crossing the N茅el transition temperature of CrPS$_4$, a layered antiferromagnetic semiconductor. This luminescent transition occurs above the lowest absorption level. We attribute the optical transitions to ex… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2405.17144v1-abstract-full').style.display = 'inline'; document.getElementById('2405.17144v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2405.17144v1-abstract-full" style="display: none;"> Two-dimensional van der Waals magnets show strong interconnection between their electrical, magnetic, and structural properties. Here we reveal the emergence of a luminescent transition upon crossing the N茅el transition temperature of CrPS$_4$, a layered antiferromagnetic semiconductor. This luminescent transition occurs above the lowest absorption level. We attribute the optical transitions to excited states of the t$_{\rm 2g}$ orbitals of the Cr$^{3+}$ ions, which are influenced by the distortion of the octahedral crystal field. Specifically, we find at the crossing of the N茅el temperature changes the distortion from an anti-polar to polar arrangement, thereby not only activating an additional luminescent pathway but also inducing a significant in-plane static dipole moment detected by a marked enhancement in the intensity of the second harmonic generation. Our findings suggest the presence of a multiferroic state in CrPS$_4$ below the N茅el temperature. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2405.17144v1-abstract-full').style.display = 'none'; document.getElementById('2405.17144v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 27 May, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2024. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2308.08355">arXiv:2308.08355</a> <span> [<a href="https://arxiv.org/pdf/2308.08355">pdf</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Materials Science">cond-mat.mtrl-sci</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1038/s41467-023-40723-x">10.1038/s41467-023-40723-x <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Multiple antiferromagnetic phases and magnetic anisotropy in exfoliated CrBr$_3$ multilayers </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Yao%2C+F">Fengrui Yao</a>, <a href="/search/cond-mat?searchtype=author&query=Multian%2C+V">Volodymyr Multian</a>, <a href="/search/cond-mat?searchtype=author&query=Wang%2C+Z">Zhe Wang</a>, <a href="/search/cond-mat?searchtype=author&query=Ubrig%2C+N">Nicolas Ubrig</a>, <a href="/search/cond-mat?searchtype=author&query=Teyssier%2C+J">J茅r茅mie Teyssier</a>, <a href="/search/cond-mat?searchtype=author&query=Wu%2C+F">Fan Wu</a>, <a href="/search/cond-mat?searchtype=author&query=Giannini%2C+E">Enrico Giannini</a>, <a href="/search/cond-mat?searchtype=author&query=Gibertini%2C+M">Marco Gibertini</a>, <a href="/search/cond-mat?searchtype=author&query=Guti%C3%A9rrez-Lezama%2C+I">Ignacio Guti茅rrez-Lezama</a>, <a href="/search/cond-mat?searchtype=author&query=Morpurgo%2C+A+F">Alberto F. Morpurgo</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2308.08355v1-abstract-short" style="display: inline;"> In twisted two-dimensional (2D) magnets, the stacking dependence of the magnetic exchange interaction can lead to regions of ferromagnetic and antiferromagnetic interlayer order, separated by non-collinear, skyrmion-like spin textures. Recent experimental searches for these textures have focused on CrI$_3$, known to exhibit either ferromagnetic or antiferromagnetic interlayer order, depending on l… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2308.08355v1-abstract-full').style.display = 'inline'; document.getElementById('2308.08355v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2308.08355v1-abstract-full" style="display: none;"> In twisted two-dimensional (2D) magnets, the stacking dependence of the magnetic exchange interaction can lead to regions of ferromagnetic and antiferromagnetic interlayer order, separated by non-collinear, skyrmion-like spin textures. Recent experimental searches for these textures have focused on CrI$_3$, known to exhibit either ferromagnetic or antiferromagnetic interlayer order, depending on layer stacking. However, the very strong uniaxial anisotropy of CrI$_3$ disfavors smooth non-collinear phases in twisted bilayers. Here, we report the experimental observation of three distinct magnetic phases -- one ferromagnetic and two antiferromagnetic -- in exfoliated CrBr$_3$ multilayers, and reveal that the uniaxial anisotropy is significantly smaller than in CrI$_3$. These results are obtained by magnetoconductance measurements on CrBr$_3$ tunnel barriers and Raman spectroscopy, in conjunction with density functional theory calculations, which enable us to identify the stackings responsible for the different interlayer magnetic couplings. The detection of all locally stable magnetic states predicted to exist in CrBr$_3$ and the excellent agreement found between theory and experiments, provide complete information on the stacking-dependent interlayer exchange energy and establish twisted bilayer CrBr$_3$ as an ideal system to deterministically create non-collinear magnetic phases. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2308.08355v1-abstract-full').style.display = 'none'; document.getElementById('2308.08355v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 16 August, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2023. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2304.12712">arXiv:2304.12712</a> <span> [<a href="https://arxiv.org/pdf/2304.12712">pdf</a>, <a href="https://arxiv.org/format/2304.12712">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1021/acs.nanolett.3c02274">10.1021/acs.nanolett.3c02274 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Magnetism-induced band-edge shift as mechanism for magnetoconductance in CrPS$_4$ transistors </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Wu%2C+F">Fan Wu</a>, <a href="/search/cond-mat?searchtype=author&query=Gibertini%2C+M">Marco Gibertini</a>, <a href="/search/cond-mat?searchtype=author&query=Watanabe%2C+K">Kenji Watanabe</a>, <a href="/search/cond-mat?searchtype=author&query=Taniguchi%2C+T">Takashi Taniguchi</a>, <a href="/search/cond-mat?searchtype=author&query=Guti%C3%A9rrez-Lezama%2C+I">Ignacio Guti茅rrez-Lezama</a>, <a href="/search/cond-mat?searchtype=author&query=Ubrig%2C+N">Nicolas Ubrig</a>, <a href="/search/cond-mat?searchtype=author&query=Morpurgo%2C+A+F">Alberto F. Morpurgo</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2304.12712v2-abstract-short" style="display: inline;"> Transistors realized on 2D antiferromagnetic semiconductor CrPS$_4$ exhibit large magnetoconductance, due to magnetic-field-induced changes in magnetic state. The microscopic mechanism coupling conductance and magnetic state is not understood. We identify it by analyzing the evolution of the parameters determining the transistor behavior -- carrier mobility and threshold voltage -- with temperatur… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2304.12712v2-abstract-full').style.display = 'inline'; document.getElementById('2304.12712v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2304.12712v2-abstract-full" style="display: none;"> Transistors realized on 2D antiferromagnetic semiconductor CrPS$_4$ exhibit large magnetoconductance, due to magnetic-field-induced changes in magnetic state. The microscopic mechanism coupling conductance and magnetic state is not understood. We identify it by analyzing the evolution of the parameters determining the transistor behavior -- carrier mobility and threshold voltage -- with temperature and magnetic field. For temperatures T near the N茅el temperature $T_N$, the magnetoconductance originates from a mobility increase due to the applied magnetic field that reduces spin fluctuation induced disorder. For $T << T_N$, instead, what changes is the threshold voltage, so that increasing the field at fixed gate voltage increases the density of accumulated electrons. The phenomenon is explained by a conduction band-edge shift correctly predicted by \emph{ab-initio} calculations. Our results demonstrate that the bandstructure of CrPS$_4$ depends on its magnetic state and reveal a mechanism for magnetoconductance that had not been identified earlier. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2304.12712v2-abstract-full').style.display = 'none'; document.getElementById('2304.12712v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 21 August, 2023; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 25 April, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 2023. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2302.11967">arXiv:2302.11967</a> <span> [<a href="https://arxiv.org/pdf/2302.11967">pdf</a>, <a href="https://arxiv.org/format/2302.11967">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Materials Science">cond-mat.mtrl-sci</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Applied Physics">physics.app-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1002/adma.202211993">10.1002/adma.202211993 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Full control of solid-state electrolytes for electrostatic gating </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Cao%2C+C">Chuanwu Cao</a>, <a href="/search/cond-mat?searchtype=author&query=Melegari%2C+M">Margherita Melegari</a>, <a href="/search/cond-mat?searchtype=author&query=Philippi%2C+M">Marc Philippi</a>, <a href="/search/cond-mat?searchtype=author&query=Domaretskiy%2C+D">Daniil Domaretskiy</a>, <a href="/search/cond-mat?searchtype=author&query=Ubrig%2C+N">Nicolas Ubrig</a>, <a href="/search/cond-mat?searchtype=author&query=Guti%C3%A9rrez-Lezama%2C+I">Ignacio Guti茅rrez-Lezama</a>, <a href="/search/cond-mat?searchtype=author&query=Morpurgo%2C+A+F">Alberto F. Morpurgo</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2302.11967v1-abstract-short" style="display: inline;"> Ionic gating is a powerful technique to realize field-effect transistors (FETs) enabling experiments not possible otherwise. So far, ionic gating has relied on the use of top-electrolyte gates, which pose experimental constraints and make device fabrication complex. Promising results obtained recently in FETs based on solid-state electrolytes remain plagued by spurious phenomena of unknown origin,… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2302.11967v1-abstract-full').style.display = 'inline'; document.getElementById('2302.11967v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2302.11967v1-abstract-full" style="display: none;"> Ionic gating is a powerful technique to realize field-effect transistors (FETs) enabling experiments not possible otherwise. So far, ionic gating has relied on the use of top-electrolyte gates, which pose experimental constraints and make device fabrication complex. Promising results obtained recently in FETs based on solid-state electrolytes remain plagued by spurious phenomena of unknown origin, preventing proper transistor operation, and causing limited control and reproducibility. Here we explore a class of solid-state electrolytes for gating (Lithium-ion conducting glass-ceramics, LICGCs), identify the processes responsible for the spurious phenomena and irreproducible behavior,and demonstrate properly functioning transistors exhibiting high density ambipolar operation with gate capacitance of ~20-50 $渭$F/cm$^2$ (depending on the polarity of the accumulated charges). Using two-dimensional semiconducting transition-metal dichalcogenides we demonstrate the ability to implement ionic-gate spectroscopy to determine the semiconducting bandgap, and to accumulate electron densities above 10$^{14}$ cm$^{-2}$, resulting in gate-induced superconductivity in MoS$_2$ multilayers. As LICGCs are implemented in a back-gate configuration, they leave the surface of the material exposed, enabling the use of surface-sensitive techniques (such as scanning tunneling microscopy and photoemission spectroscopy) impossible so far in ionic-liquid gated devices. They also allow double ionic gated devices providing independent control of charge density and electric field. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2302.11967v1-abstract-full').style.display = 'none'; document.getElementById('2302.11967v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 23 February, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2023. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2301.10535">arXiv:2301.10535</a> <span> [<a href="https://arxiv.org/pdf/2301.10535">pdf</a>, <a href="https://arxiv.org/format/2301.10535">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Materials Science">cond-mat.mtrl-sci</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1002/adma.202211653">10.1002/adma.202211653 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Gate-controlled Magnetotransport and Electrostatic Modulation of Magnetism in 2D magnetic semiconductor CrPS$_4$ </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Wu%2C+F">Fan Wu</a>, <a href="/search/cond-mat?searchtype=author&query=Gibertini%2C+M">Marco Gibertini</a>, <a href="/search/cond-mat?searchtype=author&query=Watanabe%2C+K">Kenji Watanabe</a>, <a href="/search/cond-mat?searchtype=author&query=Taniguchi%2C+T">Takashi Taniguchi</a>, <a href="/search/cond-mat?searchtype=author&query=Guti%C3%A9rrez-Lezama%2C+I">Ignacio Guti茅rrez-Lezama</a>, <a href="/search/cond-mat?searchtype=author&query=Ubrig%2C+N">Nicolas Ubrig</a>, <a href="/search/cond-mat?searchtype=author&query=Morpurgo%2C+A+F">Alberto F. Morpurgo</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2301.10535v2-abstract-short" style="display: inline;"> Using field-effect transistors (FETs) to explore atomically thin magnetic semiconductors with transport measurements is difficult, because the very narrow bands of most 2D magnetic semiconductors cause carrier localization, preventing transistor operation. Here, we show that exfoliated layers of CrPS$_4$ -- a 2D layered antiferromagnetic semiconductor whose bandwidth approaches 1 eV -- allow the r… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2301.10535v2-abstract-full').style.display = 'inline'; document.getElementById('2301.10535v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2301.10535v2-abstract-full" style="display: none;"> Using field-effect transistors (FETs) to explore atomically thin magnetic semiconductors with transport measurements is difficult, because the very narrow bands of most 2D magnetic semiconductors cause carrier localization, preventing transistor operation. Here, we show that exfoliated layers of CrPS$_4$ -- a 2D layered antiferromagnetic semiconductor whose bandwidth approaches 1 eV -- allow the realization of FETs that operate properly down to cryogenic temperature. Using these devices, we perform conductance measurements as a function of temperature and magnetic field, to determine the full magnetic phase diagram, which includes a spin-flop and a spin-flip phase. We find that the magnetoconductance depends strongly on gate voltage, reaching values as high as 5000 % near the threshold for electron conduction. The gate voltage also allows the magnetic states to be tuned, despite the relatively large thickness of the CrPS$_4$ multilayers employed in our study. Our results show the need to employ 2D magnetic semiconductors with sufficiently large bandwidth to realize properly functioning transistors, and identify a candidate material to realize a fully gate-tunable half-metallic conductor. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2301.10535v2-abstract-full').style.display = 'none'; document.getElementById('2301.10535v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 2 May, 2023; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 25 January, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2023. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted for publication in Advanced Materials</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Advanced Materials 2023 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2211.01192">arXiv:2211.01192</a> <span> [<a href="https://arxiv.org/pdf/2211.01192">pdf</a>, <a href="https://arxiv.org/format/2211.01192">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Strongly Correlated Electrons">cond-mat.str-el</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Materials Science">cond-mat.mtrl-sci</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevLett.131.046401">10.1103/PhysRevLett.131.046401 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Observation of flat $螕$ moir茅 bands in twisted bilayer WSe$_2$ </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Gatti%2C+G">Gianmarco Gatti</a>, <a href="/search/cond-mat?searchtype=author&query=Issing%2C+J">Julia Issing</a>, <a href="/search/cond-mat?searchtype=author&query=Rademaker%2C+L">Louk Rademaker</a>, <a href="/search/cond-mat?searchtype=author&query=Margot%2C+F">Florian Margot</a>, <a href="/search/cond-mat?searchtype=author&query=de+Jong%2C+T+A">Tobias A. de Jong</a>, <a href="/search/cond-mat?searchtype=author&query=van+der+Molen%2C+S+J">Sense Jan van der Molen</a>, <a href="/search/cond-mat?searchtype=author&query=Teyssier%2C+J">J茅r茅mie Teyssier</a>, <a href="/search/cond-mat?searchtype=author&query=Kim%2C+T+K">Timur K. Kim</a>, <a href="/search/cond-mat?searchtype=author&query=Watson%2C+M+D">Matthew D. Watson</a>, <a href="/search/cond-mat?searchtype=author&query=Cacho%2C+C">Cephise Cacho</a>, <a href="/search/cond-mat?searchtype=author&query=Dudin%2C+P">Pavel Dudin</a>, <a href="/search/cond-mat?searchtype=author&query=Avila%2C+J">Jos茅 Avila</a>, <a href="/search/cond-mat?searchtype=author&query=Edwards%2C+K+C">Kumara Cordero Edwards</a>, <a href="/search/cond-mat?searchtype=author&query=Paruch%2C+P">Patrycja Paruch</a>, <a href="/search/cond-mat?searchtype=author&query=Ubrig%2C+N">Nicolas Ubrig</a>, <a href="/search/cond-mat?searchtype=author&query=Guti%C3%A9rrez-Lezama%2C+I">Ignacio Guti茅rrez-Lezama</a>, <a href="/search/cond-mat?searchtype=author&query=Morpurgo%2C+A">Alberto Morpurgo</a>, <a href="/search/cond-mat?searchtype=author&query=Tamai%2C+A">Anna Tamai</a>, <a href="/search/cond-mat?searchtype=author&query=Baumberger%2C+F">Felix Baumberger</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2211.01192v1-abstract-short" style="display: inline;"> The recent observation of correlated phases in transition metal dichalcogenide moir茅 systems at integer and fractional filling promises new insight into metal-insulator transitions and the unusual states of matter that can emerge near such transitions. Here, we combine real- and momentum-space mapping techniques to study moir茅 superlattice effects in 57.4$^{\circ}$ twisted WSe$_2$ (tWSe$_2$). Our… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2211.01192v1-abstract-full').style.display = 'inline'; document.getElementById('2211.01192v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2211.01192v1-abstract-full" style="display: none;"> The recent observation of correlated phases in transition metal dichalcogenide moir茅 systems at integer and fractional filling promises new insight into metal-insulator transitions and the unusual states of matter that can emerge near such transitions. Here, we combine real- and momentum-space mapping techniques to study moir茅 superlattice effects in 57.4$^{\circ}$ twisted WSe$_2$ (tWSe$_2$). Our data reveal a split-off flat band that derives from the monolayer $螕$ states. Using advanced data analysis, we directly quantify the moir茅 potential from our data. We further demonstrate that the global valence band maximum in tWSe$_2$ is close in energy to this flat band but derives from the monolayer K-states which show weaker superlattice effects. These results constrain theoretical models and open the perspective that $螕$-valley flat bands might be involved in the correlated physics of twisted WSe$_2$. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2211.01192v1-abstract-full').style.display = 'none'; document.getElementById('2211.01192v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 2 November, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2022. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2204.10010">arXiv:2204.10010</a> <span> [<a href="https://arxiv.org/pdf/2204.10010">pdf</a>, <a href="https://arxiv.org/format/2204.10010">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1021/acs.nanolett.2c01361">10.1021/acs.nanolett.2c01361 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Probing magnetism in exfoliated VI$_3$ layers with magnetotransport </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Soler-Delgado%2C+D">David Soler-Delgado</a>, <a href="/search/cond-mat?searchtype=author&query=Yao%2C+F">Feng-rui Yao</a>, <a href="/search/cond-mat?searchtype=author&query=Dumcenco%2C+D">Dumitru Dumcenco</a>, <a href="/search/cond-mat?searchtype=author&query=Giannini%2C+E">Enrico Giannini</a>, <a href="/search/cond-mat?searchtype=author&query=Li%2C+J">Jiaruo Li</a>, <a href="/search/cond-mat?searchtype=author&query=Occhialini%2C+C+A">Connor A. Occhialini</a>, <a href="/search/cond-mat?searchtype=author&query=Comin%2C+R">Riccardo Comin</a>, <a href="/search/cond-mat?searchtype=author&query=Ubrig%2C+N">Nicolas Ubrig</a>, <a href="/search/cond-mat?searchtype=author&query=Morpurgo%2C+A+F">Alberto F. Morpurgo</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2204.10010v2-abstract-short" style="display: inline;"> We perform magnetotransport experiments on VI$_3$ multilayers, to investigate the relation between ferromagnetism in bulk and in exfoliated layers. The magnetoconductance measured on field-effect transistors and tunnel barriers shows that the Curie temperature of exfoliated multilayers is $T_C$ = 57 K, larger than in bulk ($T_{\rm C,bulk}$ = 50 K). Below $T \approx$ 40 K, we observe an unusual evo… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2204.10010v2-abstract-full').style.display = 'inline'; document.getElementById('2204.10010v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2204.10010v2-abstract-full" style="display: none;"> We perform magnetotransport experiments on VI$_3$ multilayers, to investigate the relation between ferromagnetism in bulk and in exfoliated layers. The magnetoconductance measured on field-effect transistors and tunnel barriers shows that the Curie temperature of exfoliated multilayers is $T_C$ = 57 K, larger than in bulk ($T_{\rm C,bulk}$ = 50 K). Below $T \approx$ 40 K, we observe an unusual evolution of the tunneling magnetoconductance, analogous to the phenomenology observed in bulk. Comparing the magnetoconductance measured for fields applied in- or out-of-plane corroborates the analogy, allows us to determine that the orientation of the easy-axis in multilayers is similar to that in bulk, and suggests that the in-plane component of the magnetization points in different directions in different layers. Besides establishing that the magnetic state of bulk and multilayers are similar, our experiments illustrate the complementarity of magnetotransport and magneto-optical measurements to probe magnetism in 2D materials. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2204.10010v2-abstract-full').style.display = 'none'; document.getElementById('2204.10010v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 3 August, 2022; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 21 April, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 2022. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Nano Letters 2022 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2202.11427">arXiv:2202.11427</a> <span> [<a href="https://arxiv.org/pdf/2202.11427">pdf</a>, <a href="https://arxiv.org/format/2202.11427">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Materials Science">cond-mat.mtrl-sci</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1002/adma.202109759">10.1002/adma.202109759 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Quasi 1D electronic transport in a 2D magnetic semiconductor </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Wu%2C+F">Fan Wu</a>, <a href="/search/cond-mat?searchtype=author&query=Guti%C3%A9rrez-Lezama%2C+I">Ignacio Guti茅rrez-Lezama</a>, <a href="/search/cond-mat?searchtype=author&query=Lop%C3%A9z-Paz%2C+S+A">Sara A. Lop茅z-Paz</a>, <a href="/search/cond-mat?searchtype=author&query=Gibertini%2C+M">Marco Gibertini</a>, <a href="/search/cond-mat?searchtype=author&query=Watanabe%2C+K">Kenji Watanabe</a>, <a href="/search/cond-mat?searchtype=author&query=Taniguchi%2C+T">Takashi Taniguchi</a>, <a href="/search/cond-mat?searchtype=author&query=von+Rohr%2C+F+O">Fabian O. von Rohr</a>, <a href="/search/cond-mat?searchtype=author&query=Ubrig%2C+N">Nicolas Ubrig</a>, <a href="/search/cond-mat?searchtype=author&query=Morpurgo%2C+A+F">Alberto F. Morpurgo</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2202.11427v1-abstract-short" style="display: inline;"> We investigate electronic transport through exfoliated multilayers of CrSBr, a 2D semiconductor that is attracting attention because of its magnetic properties. We find an extremely pronounced anisotropy that manifests itself in qualitative and quantitative differences of all quantities measured along the in-plane \textit{a} and \textit{b} crystallographic directions. In particular, we observe a q… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2202.11427v1-abstract-full').style.display = 'inline'; document.getElementById('2202.11427v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2202.11427v1-abstract-full" style="display: none;"> We investigate electronic transport through exfoliated multilayers of CrSBr, a 2D semiconductor that is attracting attention because of its magnetic properties. We find an extremely pronounced anisotropy that manifests itself in qualitative and quantitative differences of all quantities measured along the in-plane \textit{a} and \textit{b} crystallographic directions. In particular, we observe a qualitatively different dependence of the conductivities $蟽_a$ and $蟽_b$ on temperature and gate voltage, accompanied by orders of magnitude differences in their values ($蟽_b$/$蟽_a \approx 3\cdot10^2-10^5$ at low temperature and large negative gate voltage). We also find a different behavior of the longitudinal magnetoresistance in the two directions, and the complete absence of the Hall effect in transverse resistance measurements. These observations appear not to be compatible with a description in terms of conventional band transport of a 2D doped semiconductor. The observed phenomenology -- together with unambiguous signatures of a 1D van Hove singularity that we detect in energy resolved photocurrent measurements -- indicate that electronic transport through CrSBr multilayers is better interpreted by considering the system as formed by weakly and incoherently coupled 1D wires, than by conventional 2D band transport. We conclude that CrSBr is the first 2D semiconductor to show distinctly quasi 1D electronic transport properties. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2202.11427v1-abstract-full').style.display = 'none'; document.getElementById('2202.11427v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 23 February, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2022. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted for publication in Advanced Materials</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Adv.Mater.2022, 34, 2109759 (2022) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2201.01264">arXiv:2201.01264</a> <span> [<a href="https://arxiv.org/pdf/2201.01264">pdf</a>, <a href="https://arxiv.org/format/2201.01264">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Materials Science">cond-mat.mtrl-sci</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1038/s41467-022-31605-9">10.1038/s41467-022-31605-9 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Light sources with bias tunable spectrum based on van der Waals interface transistors </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Henck%2C+H">Hugo Henck</a>, <a href="/search/cond-mat?searchtype=author&query=Mauro%2C+D">Diego Mauro</a>, <a href="/search/cond-mat?searchtype=author&query=Domaretskiy%2C+D">Daniil Domaretskiy</a>, <a href="/search/cond-mat?searchtype=author&query=Philippi%2C+M">Marc Philippi</a>, <a href="/search/cond-mat?searchtype=author&query=Memaran%2C+S">Shahriar Memaran</a>, <a href="/search/cond-mat?searchtype=author&query=Zheng%2C+W">Wenkai Zheng</a>, <a href="/search/cond-mat?searchtype=author&query=Lu%2C+Z">Zhengguang Lu</a>, <a href="/search/cond-mat?searchtype=author&query=Shcherbakov%2C+D">Dmitry Shcherbakov</a>, <a href="/search/cond-mat?searchtype=author&query=Lau%2C+C+N">Chun Ning Lau</a>, <a href="/search/cond-mat?searchtype=author&query=Smirnov%2C+D">Dmitry Smirnov</a>, <a href="/search/cond-mat?searchtype=author&query=Balicas%2C+L">Luis Balicas</a>, <a href="/search/cond-mat?searchtype=author&query=Watanabe%2C+K">Kenji Watanabe</a>, <a href="/search/cond-mat?searchtype=author&query=Fal%27ko%2C+V+I">Vladimir I. Fal'ko</a>, <a href="/search/cond-mat?searchtype=author&query=Guti%C3%A9rrez-Lezama%2C+I">Ignacio Guti茅rrez-Lezama</a>, <a href="/search/cond-mat?searchtype=author&query=Ubrig%2C+N">Nicolas Ubrig</a>, <a href="/search/cond-mat?searchtype=author&query=Morpurgo%2C+A+F">Alberto F. Morpurgo</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2201.01264v2-abstract-short" style="display: inline;"> Light-emitting electronic devices are ubiquitous in key areas of current technology, such as data communications, solid-state lighting, displays, and optical interconnects. Controlling the spectrum of the emitted light electrically, by simply acting on the device bias conditions, is an important goal with potential technological repercussions. However, identifying a material platform enabling broa… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2201.01264v2-abstract-full').style.display = 'inline'; document.getElementById('2201.01264v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2201.01264v2-abstract-full" style="display: none;"> Light-emitting electronic devices are ubiquitous in key areas of current technology, such as data communications, solid-state lighting, displays, and optical interconnects. Controlling the spectrum of the emitted light electrically, by simply acting on the device bias conditions, is an important goal with potential technological repercussions. However, identifying a material platform enabling broad electrical tuning of the spectrum of electroluminescent devices remains challenging. Here, we propose light-emitting field-effect transistors based on van der Waals interfaces of atomically thin semiconductors as a promising class of devices to achieve this goal. We demonstrate that large spectral changes in room-temperature electroluminescence can be controlled both at the device assembly stage -- by suitably selecting the material forming the interfaces -- and on-chip, by changing the bias to modify the device operation point. Even though the precise relation between device bias and kinetics of the radiative transitions remains to be understood, our experiments show that the physical mechanism responsible for light emission is robust, making these devices compatible with simple large areas device production methods. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2201.01264v2-abstract-full').style.display = 'none'; document.getElementById('2201.01264v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 8 July, 2022; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 4 January, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2022. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Report number:</span> 10.1038/s41467-022-31605-9 </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Nature Communications 13, 3917 (2022) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2108.06117">arXiv:2108.06117</a> <span> [<a href="https://arxiv.org/pdf/2108.06117">pdf</a>, <a href="https://arxiv.org/format/2108.06117">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1038/s41565-022-01183-4">10.1038/s41565-022-01183-4 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Quenching the band gap of 2D semiconductors with a perpendicular electric field </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Domaretskiy%2C+D">Daniil Domaretskiy</a>, <a href="/search/cond-mat?searchtype=author&query=Philippi%2C+M">Marc Philippi</a>, <a href="/search/cond-mat?searchtype=author&query=Gibertini%2C+M">Marco Gibertini</a>, <a href="/search/cond-mat?searchtype=author&query=Ubrig%2C+N">Nicolas Ubrig</a>, <a href="/search/cond-mat?searchtype=author&query=Guti%C3%A9rrez-Lezama%2C+I">Ignacio Guti茅rrez-Lezama</a>, <a href="/search/cond-mat?searchtype=author&query=Morpurgo%2C+A+F">Alberto F. Morpurgo</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2108.06117v1-abstract-short" style="display: inline;"> The electronic band structure of atomically thin semiconductors can be tuned by the application of a perpendicular electric field. The principle was demonstrated experimentally shortly after the discovery of graphene by opening a finite band gap in graphene bilayers, which naturally are zero-gap semiconductors. So far, however, the same principle could not be employed to control a broader class of… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2108.06117v1-abstract-full').style.display = 'inline'; document.getElementById('2108.06117v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2108.06117v1-abstract-full" style="display: none;"> The electronic band structure of atomically thin semiconductors can be tuned by the application of a perpendicular electric field. The principle was demonstrated experimentally shortly after the discovery of graphene by opening a finite band gap in graphene bilayers, which naturally are zero-gap semiconductors. So far, however, the same principle could not be employed to control a broader class of materials, because the required electric fields are beyond reach in current devices. To overcome this limitation, we have realized double ionic gated transistors that enable the application of very large electric fields. Using these devices, we show that the band gap of few-layer semiconducting transition metal dichalcogenides can be continuously suppressed from 1.5 eV to zero. Our results illustrate an unprecedented level of control of the band structures of 2D semiconductors, which is important for future research and applications. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2108.06117v1-abstract-full').style.display = 'none'; document.getElementById('2108.06117v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 13 August, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2021. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Submitted paper</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Nature Nanotechnology, tbd (2022) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2106.13930">arXiv:2106.13930</a> <span> [<a href="https://arxiv.org/pdf/2106.13930">pdf</a>, <a href="https://arxiv.org/format/2106.13930">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Materials Science">cond-mat.mtrl-sci</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1038/s41467-021-26973-7">10.1038/s41467-021-26973-7 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Magnetization dependent tunneling conductance of ferromagnetic barriers </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Wang%2C+Z">Zhe Wang</a>, <a href="/search/cond-mat?searchtype=author&query=Guti%C3%A9rrez-Lezama%2C+I">Ignacio Guti茅rrez-Lezama</a>, <a href="/search/cond-mat?searchtype=author&query=Dumcenco%2C+D">Dumitru Dumcenco</a>, <a href="/search/cond-mat?searchtype=author&query=Ubrig%2C+N">Nicolas Ubrig</a>, <a href="/search/cond-mat?searchtype=author&query=Taniguchi%2C+T">Takashi Taniguchi</a>, <a href="/search/cond-mat?searchtype=author&query=Watanabe%2C+K">Kenji Watanabe</a>, <a href="/search/cond-mat?searchtype=author&query=Giannini%2C+E">Enrico Giannini</a>, <a href="/search/cond-mat?searchtype=author&query=Gibertini%2C+M">Marco Gibertini</a>, <a href="/search/cond-mat?searchtype=author&query=Morpurgo%2C+A+F">Alberto F. Morpurgo</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2106.13930v1-abstract-short" style="display: inline;"> Recent experiments on van der Waals antiferrmagnets such as CrI3, CrCl3 and MnPS3 have shown that using atomically thin layers as tunnel barriers and measuring the temperature ($T$) and magnetic field ($H$) dependence of the conductance allows their magnetic phase diagram to be mapped. In contrast, barriers made of CrBr3 -- the sole van der Waals ferromagnet investigated in this way -- were found… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2106.13930v1-abstract-full').style.display = 'inline'; document.getElementById('2106.13930v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2106.13930v1-abstract-full" style="display: none;"> Recent experiments on van der Waals antiferrmagnets such as CrI3, CrCl3 and MnPS3 have shown that using atomically thin layers as tunnel barriers and measuring the temperature ($T$) and magnetic field ($H$) dependence of the conductance allows their magnetic phase diagram to be mapped. In contrast, barriers made of CrBr3 -- the sole van der Waals ferromagnet investigated in this way -- were found to exhibit small and featureless magnetoconductance, seemingly carrying little information about magnetism. Here we show that -- despite these early results -- the conductance of CrBr3 tunnel barriers does provide detailed information about the magnetic state of atomically thin CrBr3 crystals for $T$ both above and below the Curie temperature ($T_C = 32$ K). Our analysis establishes that the tunneling conductance depends on $H$ and $T$ exclusively through the magnetization $M(H,T)$, over the entire temperature range investigated (2-50 K). The phenomenon is reproduced in detail by the spin-dependent Fowler-Nordheim model for tunneling, and is a direct manifestation of the spin splitting of the CrBr3 conduction band. These findings demonstrate that the investigation of magnetism by tunneling conductance measurements is not limited to antiferromagnets, but can also be applied to ferromagnetic materials. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2106.13930v1-abstract-full').style.display = 'none'; document.getElementById('2106.13930v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 25 June, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2021. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Nat Commun 12, 6659 (2021) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2106.12419">arXiv:2106.12419</a> <span> [<a href="https://arxiv.org/pdf/2106.12419">pdf</a>, <a href="https://arxiv.org/format/2106.12419">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Applied Physics">physics.app-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1088/2053-1583/ac171c">10.1088/2053-1583/ac171c <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Identifying atomically thin crystals with diffusively reflected light </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Domaretskiy%2C+D">D. Domaretskiy</a>, <a href="/search/cond-mat?searchtype=author&query=Ubrig%2C+N">N. Ubrig</a>, <a href="/search/cond-mat?searchtype=author&query=Guti%C3%A9rrez-Lezama%2C+I">I. Guti茅rrez-Lezama</a>, <a href="/search/cond-mat?searchtype=author&query=Tran%2C+M+K">M. K. Tran</a>, <a href="/search/cond-mat?searchtype=author&query=Morpurgo%2C+A+F">A. F. Morpurgo</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2106.12419v1-abstract-short" style="display: inline;"> The field of two-dimensional materials has been developing at an impressive pace, with atomically thin crystals of an increasing number of different compounds that have become available, together with techniques enabling their assembly into functional heterostructures. The strategy to detect these atomically thin crystals has however remained unchanged since the discovery of graphene. Such an abse… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2106.12419v1-abstract-full').style.display = 'inline'; document.getElementById('2106.12419v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2106.12419v1-abstract-full" style="display: none;"> The field of two-dimensional materials has been developing at an impressive pace, with atomically thin crystals of an increasing number of different compounds that have become available, together with techniques enabling their assembly into functional heterostructures. The strategy to detect these atomically thin crystals has however remained unchanged since the discovery of graphene. Such an absence of evolution is starting to pose problems because for many of the 2D materials of current interest the optical contrast provided by the commonly used detection procedure is insufficient to identify the presence of individual monolayers or to determine unambiguously the thickness of atomically thin multilayers. Here we explore an alternative detection strategy, in which the enhancement of optical contrast originates from the use of optically inhomogeneous substrates, leading to diffusively reflected light. Owing to its peculiar polarization properties and to its angular distribution, diffusively reflected light allows a strong contrast enhancement to be achieved through the implementation of suitable illumination-detection schemes. We validate this conclusion by carrying out a detailed quantitative analysis of optical contrast, which fully reproduces our experimental observations on over 60 WSe$_2$ mono-, bi-, and trilayers. We further validate the proposed strategy by extending our analysis to atomically thin phosphorene, InSe, and graphene crystals. Our conclusion is that the use of diffusively reflected light to detect and identify atomically thin layers is an interesting alternative to the common detection scheme based on Fabry-Perot interference, because it enables atomically thin layers to be detected on substrates others than the commonly used Si/SiO$_2$, and it may offer higher sensitivity depending on the specific 2D material considered. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2106.12419v1-abstract-full').style.display = 'none'; document.getElementById('2106.12419v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 23 June, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2021. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> 2D Mater. 8 045016 (2021) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2103.02230">arXiv:2103.02230</a> <span> [<a href="https://arxiv.org/pdf/2103.02230">pdf</a>, <a href="https://arxiv.org/format/2103.02230">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Materials Science">cond-mat.mtrl-sci</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1038/s42254-021-00317-2">10.1038/s42254-021-00317-2 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Ionic Gate Spectroscopy of 2D Semiconductors </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Guti%C3%A9rrez-Lezama%2C+I">Ignacio Guti茅rrez-Lezama</a>, <a href="/search/cond-mat?searchtype=author&query=Ubrig%2C+N">Nicolas Ubrig</a>, <a href="/search/cond-mat?searchtype=author&query=Ponomarev%2C+E">Evgeniy Ponomarev</a>, <a href="/search/cond-mat?searchtype=author&query=Morpurgo%2C+A+F">Alberto F. Morpurgo</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2103.02230v1-abstract-short" style="display: inline;"> Reliable and precise measurements of the relative energy of band edges in semiconductors are needed to determine band gaps and band offsets, as well as to establish the band diagram of devices and heterostructures. These measurements are particularly important in the field of two-dimensional materials, in which many new semiconducting systems are becoming available through exfoliation of bulk crys… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2103.02230v1-abstract-full').style.display = 'inline'; document.getElementById('2103.02230v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2103.02230v1-abstract-full" style="display: none;"> Reliable and precise measurements of the relative energy of band edges in semiconductors are needed to determine band gaps and band offsets, as well as to establish the band diagram of devices and heterostructures. These measurements are particularly important in the field of two-dimensional materials, in which many new semiconducting systems are becoming available through exfoliation of bulk crystals. For two-dimensional semiconductors, however, commonly employed techniques suffer from difficulties rooted either in the physics of these systems, or of technical nature. The very large exciton binding energy, for instance, prevents the band gap to be determined from a simple spectral analysis of photoluminescence, and the limited lateral size of atomically thin crystals makes the use of conventional scanning tunneling spectroscopy cumbersome. Ionic gate spectroscopy is a newly developed technique that exploits ionic gate field-effect transistors to determine quantitatively the relative alignment of band edges of two-dimensional semiconductors in a straightforward way, directly from transport measurements (i.e., from the transistor electrical characteristics). The technique relies on the extremely large geometrical capacitance of ionic gated devices that -- under suitable conditions -- enables a change in gate voltage to be directly related to a shift in chemical potential. Here we present an overview of ionic gate spectroscopy, and illustrate its relevance with applications to different two-dimensional semiconducting transition metal dichalcogenides and van der Waals heterostructures. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2103.02230v1-abstract-full').style.display = 'none'; document.getElementById('2103.02230v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 3 March, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2021. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Nat Rev Phys (2021) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2004.08896">arXiv:2004.08896</a> <span> [<a href="https://arxiv.org/pdf/2004.08896">pdf</a>, <a href="https://arxiv.org/format/2004.08896">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevResearch.2.023051">10.1103/PhysRevResearch.2.023051 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Giant anomalous Hall effect in quasi-two-dimensional layered antiferromagnet Co$_{1/3}$NbS$_2$ </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Tenasini%2C+G">Giulia Tenasini</a>, <a href="/search/cond-mat?searchtype=author&query=Martino%2C+E">Edoardo Martino</a>, <a href="/search/cond-mat?searchtype=author&query=Ubrig%2C+N">Nicolas Ubrig</a>, <a href="/search/cond-mat?searchtype=author&query=Ghimire%2C+N+J">Nirmal J. Ghimire</a>, <a href="/search/cond-mat?searchtype=author&query=Berger%2C+H">Helmuth Berger</a>, <a href="/search/cond-mat?searchtype=author&query=Zaharko%2C+O">Oksana Zaharko</a>, <a href="/search/cond-mat?searchtype=author&query=Wu%2C+F">Fengcheng Wu</a>, <a href="/search/cond-mat?searchtype=author&query=Mitchell%2C+J+F">J. F. Mitchell</a>, <a href="/search/cond-mat?searchtype=author&query=Martin%2C+I">Ivar Martin</a>, <a href="/search/cond-mat?searchtype=author&query=Forr%C3%B3%2C+L">L谩szl贸 Forr贸</a>, <a href="/search/cond-mat?searchtype=author&query=Morpurgo%2C+A+F">Alberto F. Morpurgo</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2004.08896v2-abstract-short" style="display: inline;"> The discovery of the anomalous Hall effect (AHE) in bulk metallic antiferromagnets (AFMs) motivates the search of the same phenomenon in two-dimensional (2D) systems, where a quantized anomalous Hall conductance can in principle be observed. Here, we present experiments on micro-fabricated devices based on Co$_{1/3}$NbS$_2$, a layered AFM that was recently found to exhibit AHE in bulk crystals bel… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2004.08896v2-abstract-full').style.display = 'inline'; document.getElementById('2004.08896v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2004.08896v2-abstract-full" style="display: none;"> The discovery of the anomalous Hall effect (AHE) in bulk metallic antiferromagnets (AFMs) motivates the search of the same phenomenon in two-dimensional (2D) systems, where a quantized anomalous Hall conductance can in principle be observed. Here, we present experiments on micro-fabricated devices based on Co$_{1/3}$NbS$_2$, a layered AFM that was recently found to exhibit AHE in bulk crystals below the N茅el temperature T$_N$ = 29 K. Transport measurements reveal a pronounced resistivity anisotropy, indicating that upon lowering temperature the electronic coupling between individual atomic layers is increasingly suppressed. The experiments also show an extremely large anomalous Hall conductivity of approximately 400 S/cm, more than one order of magnitude larger than in the bulk, which demonstrates the importance of studying the AHE in small exfoliated crystals, less affected by crystalline defects. Interestingly, the corresponding anomalous Hall conductance, when normalized to the number of contributing atomic planes, is $\sim \, 0.6 \; e^2/h$ per layer, approaching the value expected for the quantized anomalous Hall effect. The observed strong anisotropy of transport and the very large anomalous Hall conductance per layer make the properties of Co$_{1/3}$NbS$_2$ compatible with the presence of partially filled topologically non-trivial 2D bands originating from the magnetic superstructure of the antiferromagnetic state. Isolating atomically thin layers of this material and controlling their charge density may therefore provide a viable route to reveal the occurrence of the quantized AHE in a 2D AFM. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2004.08896v2-abstract-full').style.display = 'none'; document.getElementById('2004.08896v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 23 April, 2020; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 19 April, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 2020. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. Research 2, 023051 (2020) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2002.11997">arXiv:2002.11997</a> <span> [<a href="https://arxiv.org/pdf/2002.11997">pdf</a>, <a href="https://arxiv.org/format/2002.11997">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Materials Science">cond-mat.mtrl-sci</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1088/2053-1583/aba567">10.1088/2053-1583/aba567 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Flipping exciton angular momentum with chiral phonons in MoSe$_2$/WSe$_2$ heterobilayers </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Delhomme%2C+A">A. Delhomme</a>, <a href="/search/cond-mat?searchtype=author&query=Vaclavkova%2C+D">D. Vaclavkova</a>, <a href="/search/cond-mat?searchtype=author&query=Slobodeniuk%2C+A">A. Slobodeniuk</a>, <a href="/search/cond-mat?searchtype=author&query=Orlita%2C+M">M. Orlita</a>, <a href="/search/cond-mat?searchtype=author&query=Potemski%2C+M">M. Potemski</a>, <a href="/search/cond-mat?searchtype=author&query=Basko%2C+D+M">D. M. Basko</a>, <a href="/search/cond-mat?searchtype=author&query=Watanabe%2C+K">K. Watanabe</a>, <a href="/search/cond-mat?searchtype=author&query=Taniguchi%2C+T">T. Taniguchi</a>, <a href="/search/cond-mat?searchtype=author&query=Mauro%2C+D">D. Mauro</a>, <a href="/search/cond-mat?searchtype=author&query=Barreteau%2C+C">C. Barreteau</a>, <a href="/search/cond-mat?searchtype=author&query=Giannini%2C+E">E. Giannini</a>, <a href="/search/cond-mat?searchtype=author&query=Morpurgo%2C+A+F">A. F. Morpurgo</a>, <a href="/search/cond-mat?searchtype=author&query=Ubrig%2C+N">N. Ubrig</a>, <a href="/search/cond-mat?searchtype=author&query=Faugeras%2C+C">C. Faugeras</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2002.11997v1-abstract-short" style="display: inline;"> Identifying quantum numbers to label elementary excitations is essential for the correct description of light-matter interaction in solids. In monolayer semiconducting transition metal dichalcogenides (TMDs) such as MoSe$_2$ or WSe$_2$, most optoelectronic phenomena are described well by labelling electron and hole states with the spin projection along the normal to the layer (S$_z$). In contrast,… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2002.11997v1-abstract-full').style.display = 'inline'; document.getElementById('2002.11997v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2002.11997v1-abstract-full" style="display: none;"> Identifying quantum numbers to label elementary excitations is essential for the correct description of light-matter interaction in solids. In monolayer semiconducting transition metal dichalcogenides (TMDs) such as MoSe$_2$ or WSe$_2$, most optoelectronic phenomena are described well by labelling electron and hole states with the spin projection along the normal to the layer (S$_z$). In contrast, for WSe$_2$/MoSe$_2$ interfaces recent experiments show that taking S$_z$ as quantum number is not a good approximation, and spin mixing needs to be always considered. Here we argue that the correct quantum number for these systems is not S$_z$, but the $z$-component of the total angular momentum -- J$_z$ = L$_z$ + S$_z$ -- associated to the C$_3$ rotational lattice symmetry, which assumes half-integer values corresponding modulo 3 to distinct states. We validate this conclusion experimentally through the observation of strong intervalley scattering mediated by chiral optical phonons that -- despite carrying angular momentum 1 -- cause resonant intervalley transitions of excitons, with an angular momentum difference of 2. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2002.11997v1-abstract-full').style.display = 'none'; document.getElementById('2002.11997v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 27 February, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2020. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">are welcome</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> 2D Materials 7 041002 (2020) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2001.09777">arXiv:2001.09777</a> <span> [<a href="https://arxiv.org/pdf/2001.09777">pdf</a>, <a href="https://arxiv.org/format/2001.09777">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1021/acs.nanolett.9b04810">10.1021/acs.nanolett.9b04810 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Synthetic Semimetals with van der Waals Interfaces </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Reddy%2C+B+A">Bojja Aditya Reddy</a>, <a href="/search/cond-mat?searchtype=author&query=Ponomarev%2C+E">Evgeniy Ponomarev</a>, <a href="/search/cond-mat?searchtype=author&query=Guti%C3%A9rrez-Lezama%2C+I">Ignacio Guti茅rrez-Lezama</a>, <a href="/search/cond-mat?searchtype=author&query=Ubrig%2C+N">Nicolas Ubrig</a>, <a href="/search/cond-mat?searchtype=author&query=Barreteau%2C+C">C茅line Barreteau</a>, <a href="/search/cond-mat?searchtype=author&query=Giannini%2C+E">Enrico Giannini</a>, <a href="/search/cond-mat?searchtype=author&query=Morpurgo%2C+A+F">Alberto F. Morpurgo</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2001.09777v1-abstract-short" style="display: inline;"> The assembly of suitably designed van der Waals (vdW) heterostructures represents a new approach to produce artificial systems with engineered electronic properties. Here, we apply this strategy to realize synthetic semimetals based on vdW interfaces formed by two different semiconductors. Guided by existing ab-initio calculations, we select WSe$_2$ and SnSe$_2$ mono and multilayers to assemble vd… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2001.09777v1-abstract-full').style.display = 'inline'; document.getElementById('2001.09777v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2001.09777v1-abstract-full" style="display: none;"> The assembly of suitably designed van der Waals (vdW) heterostructures represents a new approach to produce artificial systems with engineered electronic properties. Here, we apply this strategy to realize synthetic semimetals based on vdW interfaces formed by two different semiconductors. Guided by existing ab-initio calculations, we select WSe$_2$ and SnSe$_2$ mono and multilayers to assemble vdW interfaces, and demonstrate the occurrence of semimetallicity by means of different transport experiments. Semimetallicity manifests itself in a finite minimum conductance upon sweeping the gate over a large range in ionic liquid gated devices, which also offer spectroscopic capabilities enabling the quantitative determination of the band overlap. The semimetallic state is additionally revealed in Hall effect measurements by the coexistence of electrons and holes, observed by either looking at the evolution of the Hall slope with sweeping the gate voltage or with lowering temperature. Finally, semimetallicity results in the low-temperature metallic conductivity of interfaces of two materials that are themselves insulating. These results demonstrate the possibility to implement a state of matter that had not yet been realized in vdW interfaces, and represent a first step towards using these interfaces to engineer topological or excitonic insulating states. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2001.09777v1-abstract-full').style.display = 'none'; document.getElementById('2001.09777v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 27 January, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2020. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Nano Lett. 2019 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1912.10345">arXiv:1912.10345</a> <span> [<a href="https://arxiv.org/pdf/1912.10345">pdf</a>, <a href="https://arxiv.org/format/1912.10345">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1038/s41563-019-0601-3">10.1038/s41563-019-0601-3 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Design of van der Waals Interfaces for Broad-Spectrum Optoelectronics </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Ubrig%2C+N">Nicolas Ubrig</a>, <a href="/search/cond-mat?searchtype=author&query=Ponomarev%2C+E">Evgeniy Ponomarev</a>, <a href="/search/cond-mat?searchtype=author&query=Zultak%2C+J">Johanna Zultak</a>, <a href="/search/cond-mat?searchtype=author&query=Domaretskiy%2C+D">Daniil Domaretskiy</a>, <a href="/search/cond-mat?searchtype=author&query=Z%C3%B3lyomi%2C+V">Viktor Z贸lyomi</a>, <a href="/search/cond-mat?searchtype=author&query=Terry%2C+D">Daniel Terry</a>, <a href="/search/cond-mat?searchtype=author&query=Howarth%2C+J">James Howarth</a>, <a href="/search/cond-mat?searchtype=author&query=Guti%C3%A9rrez-Lezama%2C+I">Ignacio Guti茅rrez-Lezama</a>, <a href="/search/cond-mat?searchtype=author&query=Zhukov%2C+A">Alexander Zhukov</a>, <a href="/search/cond-mat?searchtype=author&query=Kudrynskyi%2C+Z+R">Zakhar R. Kudrynskyi</a>, <a href="/search/cond-mat?searchtype=author&query=Kovalyuk%2C+Z+D">Zakhar D. Kovalyuk</a>, <a href="/search/cond-mat?searchtype=author&query=Patan%C3%A8%2C+A">Amalia Patan猫</a>, <a href="/search/cond-mat?searchtype=author&query=Taniguchi%2C+T">Takashi Taniguchi</a>, <a href="/search/cond-mat?searchtype=author&query=Watanabe%2C+K">Kenji Watanabe</a>, <a href="/search/cond-mat?searchtype=author&query=Gorbachev%2C+R+V">Roman V. Gorbachev</a>, <a href="/search/cond-mat?searchtype=author&query=Fal%27ko%2C+V+I">Vladimir I. Fal'ko</a>, <a href="/search/cond-mat?searchtype=author&query=Morpurgo%2C+A+F">Alberto F. Morpurgo</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1912.10345v2-abstract-short" style="display: inline;"> Van der Waals (vdW) materials offer new ways to assemble artificial electronic media with properties controlled at the design stage, by combining atomically defined layers into interfaces and heterostructures. Their potential for optoelectronics stems from the possibility to tailor the spectral response over a broad range by exploiting interlayer transitions between different compounds with an app… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1912.10345v2-abstract-full').style.display = 'inline'; document.getElementById('1912.10345v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1912.10345v2-abstract-full" style="display: none;"> Van der Waals (vdW) materials offer new ways to assemble artificial electronic media with properties controlled at the design stage, by combining atomically defined layers into interfaces and heterostructures. Their potential for optoelectronics stems from the possibility to tailor the spectral response over a broad range by exploiting interlayer transitions between different compounds with an appropriate band-edge alignment. For the interlayer transitions to be radiative, however, a serious challenge comes from details of the materials --such as lattice mismatch or even a small misalignment of the constituent layers-- that can drastically suppress the electron-photon coupling. The problem was evidenced in recent studies of heterostructures of monolayer transition metal dichalcogenides, whose band edges are located at the K-point of reciprocal space. Here we demonstrate experimentally that the solution to the interlayer coupling problem is to engineer type-II interfaces by assembling atomically thin crystals that have the bottom of the conduction band and the top of the valence band at the $螕$-point, thus avoiding any momentum mismatch. We find that this type of vdW interfaces exhibits radiative optical transition irrespective of lattice constant, rotational/translational alignment of the two layers, or whether the constituent materials are direct or indirect gap semiconductors. The result, which is robust and of general validity, drastically broadens the scope of future optoelectronics device applications based on 2D materials. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1912.10345v2-abstract-full').style.display = 'none'; document.getElementById('1912.10345v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 4 February, 2020; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 21 December, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 2019. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Nature Materials (2020) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1908.09607">arXiv:1908.09607</a> <span> [<a href="https://arxiv.org/pdf/1908.09607">pdf</a>, <a href="https://arxiv.org/format/1908.09607">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</span> </div> </div> <p class="title is-5 mathjax"> Low-temperature monoclinic layer stacking in atomically thin CrI$_3$ crystals </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Ubrig%2C+N">Nicolas Ubrig</a>, <a href="/search/cond-mat?searchtype=author&query=Wang%2C+Z">Zhe Wang</a>, <a href="/search/cond-mat?searchtype=author&query=Teyssier%2C+J">J茅r茅mie Teyssier</a>, <a href="/search/cond-mat?searchtype=author&query=Taniguchi%2C+T">Takashi Taniguchi</a>, <a href="/search/cond-mat?searchtype=author&query=Watanabe%2C+K">Kenji Watanabe</a>, <a href="/search/cond-mat?searchtype=author&query=Giannini%2C+E">Enrico Giannini</a>, <a href="/search/cond-mat?searchtype=author&query=Morpurgo%2C+A+F">Alberto F. Morpurgo</a>, <a href="/search/cond-mat?searchtype=author&query=Gibertini%2C+M">Marco Gibertini</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1908.09607v1-abstract-short" style="display: inline;"> Chromium triiodide, CrI$_3$, is emerging as a promising magnetic two-dimensional semiconductor where spins are ferromagnetically aligned within a single layer. Potential applications in spintronics arise from an antiferromagnetic ordering between adjacent layers that gives rise to spin filtering and a large magnetoresistance in tunnelling devices. This key feature appears only in thin multilayers… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1908.09607v1-abstract-full').style.display = 'inline'; document.getElementById('1908.09607v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1908.09607v1-abstract-full" style="display: none;"> Chromium triiodide, CrI$_3$, is emerging as a promising magnetic two-dimensional semiconductor where spins are ferromagnetically aligned within a single layer. Potential applications in spintronics arise from an antiferromagnetic ordering between adjacent layers that gives rise to spin filtering and a large magnetoresistance in tunnelling devices. This key feature appears only in thin multilayers and it is not inherited from bulk crystals, where instead neighbouring layers share the same ferromagnetic spin orientation. This discrepancy between bulk and thin samples is unexpected, as magnetic ordering between layers arises from exchange interactions that are local in nature and should not depend strongly on thickness. Here we solve this controversy and show through polarization resolved Raman spectroscopy that thin multilayers do not undergo a structural phase transition typical of bulk crystals. As a consequence, a different stacking pattern is present in thin and bulk samples at the temperatures at which magnetism sets in and, according to previous first-principles simulations, this results in a different interlayer magnetic ordering. Our experimental findings provide evidence for the strong interplay between stacking order and magnetism in CrI$_3$, opening interesting perspectives to design the magnetic state of van der Waals multilayers. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1908.09607v1-abstract-full').style.display = 'none'; document.getElementById('1908.09607v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 26 August, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2019. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">7 pages, 3 figures</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1902.01406">arXiv:1902.01406</a> <span> [<a href="https://arxiv.org/pdf/1902.01406">pdf</a>, <a href="https://arxiv.org/format/1902.01406">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Quantum Physics">quant-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1126/science.aav6926">10.1126/science.aav6926 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Probing magnetism in 2D materials at the nanoscale with single spin microscopy </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Thiel%2C+L">Lucas Thiel</a>, <a href="/search/cond-mat?searchtype=author&query=Wang%2C+Z">Zhe Wang</a>, <a href="/search/cond-mat?searchtype=author&query=Tschudin%2C+M+A">M盲rta A. Tschudin</a>, <a href="/search/cond-mat?searchtype=author&query=Rohner%2C+D">Dominik Rohner</a>, <a href="/search/cond-mat?searchtype=author&query=Guti%C3%A9rrez-Lezama%2C+I">Ignacio Guti茅rrez-Lezama</a>, <a href="/search/cond-mat?searchtype=author&query=Ubrig%2C+N">Nicolas Ubrig</a>, <a href="/search/cond-mat?searchtype=author&query=Gibertini%2C+M">Marco Gibertini</a>, <a href="/search/cond-mat?searchtype=author&query=Giannini%2C+E">Enrico Giannini</a>, <a href="/search/cond-mat?searchtype=author&query=Morpurgo%2C+A+F">Alberto F. Morpurgo</a>, <a href="/search/cond-mat?searchtype=author&query=Maletinsky%2C+P">Patrick Maletinsky</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1902.01406v1-abstract-short" style="display: inline;"> The recent discovery of ferromagnetism in 2D van der Waals (vdw) crystals has generated widespread interest, owing to their potential for fundamental and applied research. Advancing the understanding and applications of vdw magnets requires methods to quantitatively probe their magnetic properties on the nanoscale. Here, we report the study of atomically thin crystals of the vdw magnet CrI$_3$ dow… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1902.01406v1-abstract-full').style.display = 'inline'; document.getElementById('1902.01406v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1902.01406v1-abstract-full" style="display: none;"> The recent discovery of ferromagnetism in 2D van der Waals (vdw) crystals has generated widespread interest, owing to their potential for fundamental and applied research. Advancing the understanding and applications of vdw magnets requires methods to quantitatively probe their magnetic properties on the nanoscale. Here, we report the study of atomically thin crystals of the vdw magnet CrI$_3$ down to individual monolayers using scanning single-spin magnetometry, and demonstrate quantitative, nanoscale imaging of magnetisation, localised defects and magnetic domains. We determine the magnetisation of CrI$_3$ monolayers to be $\approx16~渭_B/$nm$^2$ and find comparable values in samples with odd numbers of layers, whereas the magnetisation vanishes when the number of layers is even. We also establish that this inscrutable even-odd effect is intimately connected to the material structure, and that structural modifications can induce switching between ferro- and anti-ferromagnetic interlayer ordering. Besides revealing new aspects of magnetism in atomically thin CrI$_3$ crystals, these results demonstrate the power of single-spin scanning magnetometry for the study of magnetism in 2D vdw magnets. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1902.01406v1-abstract-full').style.display = 'none'; document.getElementById('1902.01406v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 4 February, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2019. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Questions and comments are welcome. For further information and related job-openings, please visit www.quantum-sensing.ch</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Science 364, 973-976 (2019) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1901.08012">arXiv:1901.08012</a> <span> [<a href="https://arxiv.org/pdf/1901.08012">pdf</a>, <a href="https://arxiv.org/format/1901.08012">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Materials Science">cond-mat.mtrl-sci</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevX.9.031019">10.1103/PhysRevX.9.031019 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Enhanced electron-phonon interaction in multi-valley materials </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Ponomarev%2C+E">Evgeniy Ponomarev</a>, <a href="/search/cond-mat?searchtype=author&query=Sohier%2C+T">Thibault Sohier</a>, <a href="/search/cond-mat?searchtype=author&query=Gibertini%2C+M">Marco Gibertini</a>, <a href="/search/cond-mat?searchtype=author&query=Berger%2C+H">Helmuth Berger</a>, <a href="/search/cond-mat?searchtype=author&query=Marzari%2C+N">Nicola Marzari</a>, <a href="/search/cond-mat?searchtype=author&query=Ubrig%2C+N">Nicolas Ubrig</a>, <a href="/search/cond-mat?searchtype=author&query=Morpurgo%2C+A+F">Alberto F. Morpurgo</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1901.08012v1-abstract-short" style="display: inline;"> Through a combined theoretical and experimental effort, we uncover a yet unidentified mechanism that strengthens considerably electron-phonon coupling in materials where electron accumulation leads to population of multiple valleys. Taking atomically-thin transition-metal dichalcogenides as prototypical examples, we establish that the mechanism results from a phonon-induced out-of-phase energy shi… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1901.08012v1-abstract-full').style.display = 'inline'; document.getElementById('1901.08012v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1901.08012v1-abstract-full" style="display: none;"> Through a combined theoretical and experimental effort, we uncover a yet unidentified mechanism that strengthens considerably electron-phonon coupling in materials where electron accumulation leads to population of multiple valleys. Taking atomically-thin transition-metal dichalcogenides as prototypical examples, we establish that the mechanism results from a phonon-induced out-of-phase energy shift of the different valleys, which causes inter-valley charge transfer and reduces the effectiveness of electrostatic screening, thus enhancing electron-phonon interactions. The effect is physically robust, it can play a role in many materials and phenomena, as we illustrate by discussing experimental evidence for its relevance in the occurrence of superconductivity. (short abstract due to size limitations - full abstract in the manuscript) <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1901.08012v1-abstract-full').style.display = 'none'; document.getElementById('1901.08012v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 23 January, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2019. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">16 pages, 8 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. X 9, 031019 (2019) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1811.04629">arXiv:1811.04629</a> <span> [<a href="https://arxiv.org/pdf/1811.04629">pdf</a>, <a href="https://arxiv.org/format/1811.04629">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Materials Science">cond-mat.mtrl-sci</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1021/acs.nanolett.8b04534">10.1021/acs.nanolett.8b04534 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Microfocus laser-ARPES on encapsulated mono-, bi-, and few-layer 1T'-WTe$_2$ </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Cucchi%2C+I">Ir猫ne Cucchi</a>, <a href="/search/cond-mat?searchtype=author&query=Guti%C3%A9rrez-Lezama%2C+I">Ignacio Guti茅rrez-Lezama</a>, <a href="/search/cond-mat?searchtype=author&query=Cappelli%2C+E">Edoardo Cappelli</a>, <a href="/search/cond-mat?searchtype=author&query=Walker%2C+S+M">Siobhan McKeown Walker</a>, <a href="/search/cond-mat?searchtype=author&query=Bruno%2C+F+Y">Flavio Y. Bruno</a>, <a href="/search/cond-mat?searchtype=author&query=Tenasini%2C+G">Giulia Tenasini</a>, <a href="/search/cond-mat?searchtype=author&query=Wang%2C+L">Lin Wang</a>, <a href="/search/cond-mat?searchtype=author&query=Ubrig%2C+N">Nicolas Ubrig</a>, <a href="/search/cond-mat?searchtype=author&query=Barreteau%2C+C">C茅line Barreteau</a>, <a href="/search/cond-mat?searchtype=author&query=Giannini%2C+E">Enrico Giannini</a>, <a href="/search/cond-mat?searchtype=author&query=Gibertini%2C+M">Marco Gibertini</a>, <a href="/search/cond-mat?searchtype=author&query=Tamai%2C+A">Anna Tamai</a>, <a href="/search/cond-mat?searchtype=author&query=Morpurgo%2C+A+F">Alberto F. Morpurgo</a>, <a href="/search/cond-mat?searchtype=author&query=Baumberger%2C+F">Felix Baumberger</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1811.04629v1-abstract-short" style="display: inline;"> Two-dimensional crystals of semimetallic van der Waals materials hold much potential for the realization of novel phases, as exemplified by the recent discoveries of a polar metal in few layer 1T'-WTe$_2$ and of a quantum spin Hall state in monolayers of the same material. Understanding these phases is particularly challenging because little is known from experiment about the momentum space electr… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1811.04629v1-abstract-full').style.display = 'inline'; document.getElementById('1811.04629v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1811.04629v1-abstract-full" style="display: none;"> Two-dimensional crystals of semimetallic van der Waals materials hold much potential for the realization of novel phases, as exemplified by the recent discoveries of a polar metal in few layer 1T'-WTe$_2$ and of a quantum spin Hall state in monolayers of the same material. Understanding these phases is particularly challenging because little is known from experiment about the momentum space electronic structure of ultrathin crystals. Here, we report direct electronic structure measurements of exfoliated mono-, bi-, and few-layer 1T'-WTe$_2$ by laser-based micro-focus angle resolved photoemission. This is achieved by encapsulating with monolayer graphene a flake of WTe$_2$ comprising regions of different thickness. Our data support the recent identification of a quantum spin Hall state in monolayer 1T'-WTe$_2$ and reveal strong signatures of the broken inversion symmetry in the bilayer. We finally discuss the sensitivity of encapsulated samples to contaminants following exposure to ambient atmosphere. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1811.04629v1-abstract-full').style.display = 'none'; document.getElementById('1811.04629v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 12 November, 2018; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2018. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">14 pages, 5 figures</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1807.09029">arXiv:1807.09029</a> <span> [<a href="https://arxiv.org/pdf/1807.09029">pdf</a>, <a href="https://arxiv.org/format/1807.09029">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1063/1.5038407">10.1063/1.5038407 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Lithium-ion conducting glass ceramics for electrostatic gating </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Philippi%2C+M">Marc Philippi</a>, <a href="/search/cond-mat?searchtype=author&query=Guti%C3%A9rrez-Lezama%2C+I">Ignacio Guti茅rrez-Lezama</a>, <a href="/search/cond-mat?searchtype=author&query=Ubrig%2C+N">Nicolas Ubrig</a>, <a href="/search/cond-mat?searchtype=author&query=Morpurgo%2C+A+F">Alberto F. Morpurgo</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1807.09029v1-abstract-short" style="display: inline;"> We explore solid electrolytes for electrostatic gating using field-effect transistors (FETs) in which thin WSe$_2$ crystals are exfoliated and transferred onto a lithium-ion conducting glass ceramic substrate. For negative gate voltages ($V_G < 0$) the devices work equally well as ionic liquid gated FETs while offering specific advantages, whereas no transistor action is seen for $V_G>0$. For… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1807.09029v1-abstract-full').style.display = 'inline'; document.getElementById('1807.09029v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1807.09029v1-abstract-full" style="display: none;"> We explore solid electrolytes for electrostatic gating using field-effect transistors (FETs) in which thin WSe$_2$ crystals are exfoliated and transferred onto a lithium-ion conducting glass ceramic substrate. For negative gate voltages ($V_G < 0$) the devices work equally well as ionic liquid gated FETs while offering specific advantages, whereas no transistor action is seen for $V_G>0$. For $V_G <0$ the devices can nevertheless be driven into the ambipolar injection regime by applying a large source-drain bias, and strong electroluminescence is observed when direct band-gap WSe$_2$ monolayers are used. Detecting and imaging the emitted light is much simpler in these FETs as compared to ionic liquid gated transistors, because the semiconductor surface is exposed (i.e., not covered by another material). Our results show that solid electrolytes are complementary to existing liquid gates, as they enable experiments not possible when the semiconductor is buried under the liquid itself. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1807.09029v1-abstract-full').style.display = 'none'; document.getElementById('1807.09029v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 24 July, 2018; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2018. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Appl. Phys. Lett. 113, 033502 (2018) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1807.08282">arXiv:1807.08282</a> <span> [<a href="https://arxiv.org/pdf/1807.08282">pdf</a>, <a href="https://arxiv.org/format/1807.08282">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1021/acs.nanolett.8b02066">10.1021/acs.nanolett.8b02066 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Semiconducting van der Waals Interfaces as Artificial Semiconductors </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Ponomarev%2C+E">Evgeniy Ponomarev</a>, <a href="/search/cond-mat?searchtype=author&query=Ubrig%2C+N">Nicolas Ubrig</a>, <a href="/search/cond-mat?searchtype=author&query=Guti%C3%A9rrez-Lezama%2C+I">Ignacio Guti茅rrez-Lezama</a>, <a href="/search/cond-mat?searchtype=author&query=Berger%2C+H">Helmuth Berger</a>, <a href="/search/cond-mat?searchtype=author&query=Morpurgo%2C+A+F">Alberto F. Morpurgo</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1807.08282v1-abstract-short" style="display: inline;"> Recent technical progress demonstrates the possibility of stacking together virtually any combination of atomically thin crystals of van der Waals bonded compounds to form new types of heterostructures and interfaces. As a result, there is the need to understand at a quantitative level how the interfacial properties are determined by the properties of the constituent 2D materials. We address this… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1807.08282v1-abstract-full').style.display = 'inline'; document.getElementById('1807.08282v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1807.08282v1-abstract-full" style="display: none;"> Recent technical progress demonstrates the possibility of stacking together virtually any combination of atomically thin crystals of van der Waals bonded compounds to form new types of heterostructures and interfaces. As a result, there is the need to understand at a quantitative level how the interfacial properties are determined by the properties of the constituent 2D materials. We address this problem by studying the transport and optoelectronic response of two different interfaces based on transition-metal dichalcogenide monolayers, namely WSe2-MoSe2 and WSe2-MoS2. By exploiting the spectroscopic capabilities of ionic liquid gated transistors, we show how the conduction and valence bands of the individual monolayers determine the bands of the interface, and we establish quantitatively (directly from the measurements) the energetic alignment of the bands in the different materials as well as the magnitude of the interfacial band gap. Photoluminescence and photocurrent measurements allow us to conclude that the band gap of the WSe2-MoSe2 interface is direct in k space, whereas the gap of WSe2/MoS2 is indirect. For WSe2/MoSe2, we detect the light emitted from the decay of interlayer excitons and determine experimentally their binding energy using the values of the interfacial band gap extracted from transport measurements. The technique that we employed to reach this conclusion demonstrates a rather-general strategy for characterizing quantitatively the interfacial properties in terms of the properties of the constituent atomic layers. The results presented here further illustrate how van der Waals interfaces of two distinct 2D semiconducting materials are composite systems that truly behave as artificial semiconductors, the properties of which can be deterministically defined by the selection of the appropriate constituent semiconducting monolayers. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1807.08282v1-abstract-full').style.display = 'none'; document.getElementById('1807.08282v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 22 July, 2018; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2018. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Nano Letters 2018</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1804.09218">arXiv:1804.09218</a> <span> [<a href="https://arxiv.org/pdf/1804.09218">pdf</a>, <a href="https://arxiv.org/format/1804.09218">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1021/acsnano.7b08831">10.1021/acsnano.7b08831 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Hole Transport in Exfoliated Monolayer MoS$_2$ </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Ponomarev%2C+E">Evgeniy Ponomarev</a>, <a href="/search/cond-mat?searchtype=author&query=P%C3%A1sztor%2C+%C3%81">脕rp谩d P谩sztor</a>, <a href="/search/cond-mat?searchtype=author&query=Waelchli%2C+A">Adrien Waelchli</a>, <a href="/search/cond-mat?searchtype=author&query=Scarfato%2C+A">Alessandro Scarfato</a>, <a href="/search/cond-mat?searchtype=author&query=Ubrig%2C+N">Nicolas Ubrig</a>, <a href="/search/cond-mat?searchtype=author&query=Renner%2C+C">Christoph Renner</a>, <a href="/search/cond-mat?searchtype=author&query=Morpurgo%2C+A+F">Alberto F. Morpurgo</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1804.09218v1-abstract-short" style="display: inline;"> Ideal monolayers of common semiconducting transition metal dichalcogenides (TMDCs) such as MoS$_2$, WS$_2$, MoSe$_2$, and WSe$_2$ possess many similar electronic properties. As it is the case for all semiconductors, however, the physical response of these systems is strongly determined by defects in a way specific to each individual compound. Here we investigate the ability of exfoliated monolayer… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1804.09218v1-abstract-full').style.display = 'inline'; document.getElementById('1804.09218v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1804.09218v1-abstract-full" style="display: none;"> Ideal monolayers of common semiconducting transition metal dichalcogenides (TMDCs) such as MoS$_2$, WS$_2$, MoSe$_2$, and WSe$_2$ possess many similar electronic properties. As it is the case for all semiconductors, however, the physical response of these systems is strongly determined by defects in a way specific to each individual compound. Here we investigate the ability of exfoliated monolayers of these TMDCs to support high-quality, well-balanced ambipolar conduction, which has been demonstrated for WS$_2$, MoSe$_2$, and WSe$_2$, but not for MoS$_2$. Using ionic-liquid gated transistors we show that, contrary to WS$_2$, MoSe$_2$, and WSe$_2$, hole transport in exfoliated MoS$_2$ monolayers is systematically anomalous, exhibiting a maximum in conductivity at negative gate voltage (V$_G$) followed by a suppression of up to 100 times upon further increasing V$_G$. To understand the origin of this difference we have performed a series of experiments including the comparison of hole transport in MoS$_2$ monolayers and thicker multilayers, in exfoliated and CVD-grown monolayers, as well as gate-dependent optical measurements (Raman and photoluminescence) and scanning tunneling imaging and spectroscopy. In agreement with existing {\it ab-initio} calculations, the results of all these experiments are consistently explained in terms of defects associated to chalcogen vacancies that only in MoS$_2$ monolayers -- but not in thicker MoS$_2$ multilayers nor in monolayers of the other common semiconducting TMDCs -- create in-gap states near the top of the valence band that act as strong hole traps. Our results demonstrate the importance of studying systematically how defects determine the properties of 2D semiconducting materials and of developing methods to control them. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1804.09218v1-abstract-full').style.display = 'none'; document.getElementById('1804.09218v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 24 April, 2018; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 2018. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> ACS Nano, 2018, 12 (3), pp 2669-2676 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1801.08188">arXiv:1801.08188</a> <span> [<a href="https://arxiv.org/pdf/1801.08188">pdf</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Materials Science">cond-mat.mtrl-sci</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1038/s41467-018-04953-8">10.1038/s41467-018-04953-8 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Very Large Tunneling Magnetoresistance in Layered Magnetic Semiconductor CrI$_3$ </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Wang%2C+Z">Zhe Wang</a>, <a href="/search/cond-mat?searchtype=author&query=Guti%C3%A9rrez-Lezama%2C+I">Ignacio Guti茅rrez-Lezama</a>, <a href="/search/cond-mat?searchtype=author&query=Ubrig%2C+N">Nicolas Ubrig</a>, <a href="/search/cond-mat?searchtype=author&query=Kroner%2C+M">Martin Kroner</a>, <a href="/search/cond-mat?searchtype=author&query=Gibertini%2C+M">Marco Gibertini</a>, <a href="/search/cond-mat?searchtype=author&query=Taniguchi%2C+T">Takashi Taniguchi</a>, <a href="/search/cond-mat?searchtype=author&query=Watanabe%2C+K">Kenji Watanabe</a>, <a href="/search/cond-mat?searchtype=author&query=Imamo%C4%9Flu%2C+A">Ata莽 Imamo臒lu</a>, <a href="/search/cond-mat?searchtype=author&query=Giannini%2C+E">Enrico Giannini</a>, <a href="/search/cond-mat?searchtype=author&query=Morpurgo%2C+A+F">Alberto F. Morpurgo</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1801.08188v2-abstract-short" style="display: inline;"> Magnetic layered van der Waals crystals are an emerging class of materials giving access to new physical phenomena, as illustrated by the recent observation of 2D ferromagnetism in Cr2Ge2Te6 and CrI3. Of particular interest in semiconductors is the interplay between magnetism and transport, which has remained unexplored. Here we report first magneto-transport measurements on exfoliated CrI3 crysta… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1801.08188v2-abstract-full').style.display = 'inline'; document.getElementById('1801.08188v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1801.08188v2-abstract-full" style="display: none;"> Magnetic layered van der Waals crystals are an emerging class of materials giving access to new physical phenomena, as illustrated by the recent observation of 2D ferromagnetism in Cr2Ge2Te6 and CrI3. Of particular interest in semiconductors is the interplay between magnetism and transport, which has remained unexplored. Here we report first magneto-transport measurements on exfoliated CrI3 crystals. We find that tunneling conduction in the direction perpendicular to the crystalline planes exhibits a magnetoresistance as large as 10 000 %. The evolution of the magnetoresistance with magnetic field and temperature reveals that the phenomenon originates from multiple transitions to different magnetic states, whose possible microscopic nature is discussed on the basis of all existing experimental observations. This observed dependence of the conductance of a tunnel barrier on its magnetic state is a new phenomenon that demonstrates the presence of a strong coupling between transport and magnetism in magnetic van der Waals semiconductors. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1801.08188v2-abstract-full').style.display = 'none'; document.getElementById('1801.08188v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 28 June, 2018; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 24 January, 2018; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2018. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Nature Communications (2018) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1708.06914">arXiv:1708.06914</a> <span> [<a href="https://arxiv.org/pdf/1708.06914">pdf</a>, <a href="https://arxiv.org/format/1708.06914">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1021/acs.nanolett.7b02666">10.1021/acs.nanolett.7b02666 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Microscopic Origin of the Valley Hall Effect in Transition Metal Dichalcogenides Revealed by Wavelength Dependent Mapping </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Ubrig%2C+N">Nicolas Ubrig</a>, <a href="/search/cond-mat?searchtype=author&query=Jo%2C+S">Sanghyun Jo</a>, <a href="/search/cond-mat?searchtype=author&query=Philippi%2C+M">Marc Philippi</a>, <a href="/search/cond-mat?searchtype=author&query=Costanzo%2C+D">Davide Costanzo</a>, <a href="/search/cond-mat?searchtype=author&query=Berger%2C+H">Helmuth Berger</a>, <a href="/search/cond-mat?searchtype=author&query=Kuzmenko%2C+A+B">Alexey B. Kuzmenko</a>, <a href="/search/cond-mat?searchtype=author&query=Morpurgo%2C+A+F">Alberto F. Morpurgo</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1708.06914v2-abstract-short" style="display: inline;"> The band structure of many semiconducting monolayer transition metal dichalcogenides (TMDs) possesses two degenerate valleys, with equal and opposite Berry curvature. It has been predicted that, when illuminated with circularly polarized light, interband transitions generate an unbalanced non-equilibrium population of electrons and holes in these valleys, resulting in a finite Hall voltage at zero… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1708.06914v2-abstract-full').style.display = 'inline'; document.getElementById('1708.06914v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1708.06914v2-abstract-full" style="display: none;"> The band structure of many semiconducting monolayer transition metal dichalcogenides (TMDs) possesses two degenerate valleys, with equal and opposite Berry curvature. It has been predicted that, when illuminated with circularly polarized light, interband transitions generate an unbalanced non-equilibrium population of electrons and holes in these valleys, resulting in a finite Hall voltage at zero magnetic field when a current flows through the system. This is the so-called valley Hall effect that has recently been observed experimentally. Here, we show that this effect is mediated by photo-generated neutral excitons and charged trions, and not by inter-band transitions generating independent electrons and holes. We further demonstrate an experimental strategy, based on wavelength dependent spatial mapping of the Hall voltage, which allows the exciton and trion contributions to the valley Hall effect to be discriminated in the measurement. These results represent a significant step forward in our understanding of the microscopic origin of photo-induced valley Hall effect in semiconducting transition metal dichalcogenides, and demonstrate experimentally that composite quasi-particles, such as trions, can also possess a finite Berry curvature. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1708.06914v2-abstract-full').style.display = 'none'; document.getElementById('1708.06914v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 31 August, 2017; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 23 August, 2017; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2017. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">accepted for publication in Nano Letters</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Nano Lett., 17 (9), pp 5719-5725 (2017) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1610.00895">arXiv:1610.00895</a> <span> [<a href="https://arxiv.org/pdf/1610.00895">pdf</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Materials Science">cond-mat.mtrl-sci</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</span> </div> </div> <p class="title is-5 mathjax"> Electroluminescence from indirect band gap semiconductor ReS$_2$ </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Lezama%2C+I+G">Ignacio Guti茅rrez Lezama</a>, <a href="/search/cond-mat?searchtype=author&query=Reddy%2C+B+A">Bojja Aditya Reddy</a>, <a href="/search/cond-mat?searchtype=author&query=Ubrig%2C+N">Nicolas Ubrig</a>, <a href="/search/cond-mat?searchtype=author&query=Morpurgo%2C+A+F">Alberto F. Morpurgo</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1610.00895v1-abstract-short" style="display: inline;"> It has been recently claimed that bulk crystals of transition metal dichalcogenide (TMD) ReS$_2$ are direct band gap semiconductors, which would make this material an ideal candidate, among all TMDs, for the realization of efficient opto-electronic devices. The situation is however unclear, because even more recently an indirect transition in the photoluminescence spectra of this material has been… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1610.00895v1-abstract-full').style.display = 'inline'; document.getElementById('1610.00895v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1610.00895v1-abstract-full" style="display: none;"> It has been recently claimed that bulk crystals of transition metal dichalcogenide (TMD) ReS$_2$ are direct band gap semiconductors, which would make this material an ideal candidate, among all TMDs, for the realization of efficient opto-electronic devices. The situation is however unclear, because even more recently an indirect transition in the photoluminescence spectra of this material has been detected, whose energy is smaller than the supposed direct gap. To address this issue we exploit the properties of ionic liquid gated field-effect transistors (FETs) to investigate the gap structure of bulk ReS$_2$. Using these devices, whose high quality is demonstrated by a record high electron FET mobility of 1,100 cm$^2$/Vs at 4K, we can induce hole transport at the surface of the material and determine quantitatively the smallest band gap present in the material, irrespective of its direct or indirect nature. The value of the band gap is found to be 1.41 eV, smaller than the 1.5 eV direct optical transition but in good agreement with the energy of the indirect optical transition, providing an independent confirmation that bulk ReS$_2$ is an indirect band gap semiconductor. Nevertheless, contrary to the case of more commonly studied semiconducting TMDs (e.g., MoS$_2$, WS$_2$, etc.) in their bulk form, we also find that ReS$_2$ FETs fabricated on bulk crystals do exhibit electroluminescence when driven in the ambipolar injection regime, likely because the difference between the direct and indirect gap is only 100 meV. We conclude that ReS$_2$ does deserve more in-depth investigations in relation to possible opto-electronic applications. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1610.00895v1-abstract-full').style.display = 'none'; document.getElementById('1610.00895v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 4 October, 2016; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2016. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">To appear in 2D Materials (19 pages, 4 Figures)</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1602.01663">arXiv:1602.01663</a> <span> [<a href="https://arxiv.org/pdf/1602.01663">pdf</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1021/acs.nanolett.5b03885">10.1021/acs.nanolett.5b03885 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Ambipolar Light-Emitting Transistors on Chemical Vapor Deposited Monolayer MoS2 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Ponomarev%2C+E">Evgeniy Ponomarev</a>, <a href="/search/cond-mat?searchtype=author&query=Guti%C3%A9rrez-Lezama%2C+I">Ignacio Guti茅rrez-Lezama</a>, <a href="/search/cond-mat?searchtype=author&query=Ubrig%2C+N">Nicolas Ubrig</a>, <a href="/search/cond-mat?searchtype=author&query=Morpurgo%2C+A+F">Alberto F. Morpurgo</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1602.01663v1-abstract-short" style="display: inline;"> We realize and investigate ionic liquid gated field-effect transistors (FETs) on large-area MoS2 monolayers grown by chemical vapor deposition (CVD). Under electron accumulation, the performance of these devices is comparable to that of FETs based on exfoliated flakes. FETs on CVD-grown material, however, exhibit clear ambipolar transport, which for MoS2 monolayers had not been reported previously… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1602.01663v1-abstract-full').style.display = 'inline'; document.getElementById('1602.01663v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1602.01663v1-abstract-full" style="display: none;"> We realize and investigate ionic liquid gated field-effect transistors (FETs) on large-area MoS2 monolayers grown by chemical vapor deposition (CVD). Under electron accumulation, the performance of these devices is comparable to that of FETs based on exfoliated flakes. FETs on CVD-grown material, however, exhibit clear ambipolar transport, which for MoS2 monolayers had not been reported previously. We exploit this property to estimate the bandgap 螖 of monolayer MoS2 directly from the device transfer curves and find 螖 $\approx$ 2.4-2.7 eV. In the ambipolar injection regime, we observe electroluminescence due to exciton recombination in MoS2, originating from the region close to the hole-injecting contact. Both the observed transport properties and the behavior of the electroluminescence can be consistently understood as due to the presence of defect states at an energy of 250-300 meV above the top of the valence band, acting as deep traps for holes. Our results are of technological relevance, as they show that devices with useful optoelectronic functionality can be realized on large-area MoS2 monolayers produced by controllable and scalable techniques. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1602.01663v1-abstract-full').style.display = 'none'; document.getElementById('1602.01663v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 4 February, 2016; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2016. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Nano Lett., 2015, 15 (12), pp.8289-8294 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1510.04827">arXiv:1510.04827</a> <span> [<a href="https://arxiv.org/pdf/1510.04827">pdf</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1038/ncomms9892">10.1038/ncomms9892 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Tuning Magnetotransport in a Compensated Semimetal at the Atomic Scale </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Wang%2C+L">Lin Wang</a>, <a href="/search/cond-mat?searchtype=author&query=Guti%C3%A9rrez-Lezama%2C+I">Ignacio Guti茅rrez-Lezama</a>, <a href="/search/cond-mat?searchtype=author&query=Barreteau%2C+C">C茅line Barreteau</a>, <a href="/search/cond-mat?searchtype=author&query=Ubrig%2C+N">Nicolas Ubrig</a>, <a href="/search/cond-mat?searchtype=author&query=Giannini%2C+E">Enrico Giannini</a>, <a href="/search/cond-mat?searchtype=author&query=Morpurgo%2C+A+F">A. F. Morpurgo</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1510.04827v2-abstract-short" style="display: inline;"> Either in bulk form, or when exfoliated into atomically thin crystals, layered transition metal dichalcogenides are continuously leading to the discovery of new phenomena. The latest example is provided by 1T'-WTe$_2$, a semimetal recently found to exhibit the largest known magnetoresistance in bulk crystals, and predicted to become a two-dimensional topological insulator in strained monolayers. H… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1510.04827v2-abstract-full').style.display = 'inline'; document.getElementById('1510.04827v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1510.04827v2-abstract-full" style="display: none;"> Either in bulk form, or when exfoliated into atomically thin crystals, layered transition metal dichalcogenides are continuously leading to the discovery of new phenomena. The latest example is provided by 1T'-WTe$_2$, a semimetal recently found to exhibit the largest known magnetoresistance in bulk crystals, and predicted to become a two-dimensional topological insulator in strained monolayers. Here, we show that reducing the thickness through facile exfoliation provides an effective experimental knob to tune the electronic properties of WTe$_2$, which allows us to identify the microscopic mechanisms responsible for the observed classical and quantum magnetotransport down to the ultimate atomic scale. We find that the longitudinal resistance and the very unconventional B-dependence of the Hall resistance are reproduced quantitatively in terms of a classical two-band model for crystals as thin as six monolayers, and that for thinner crystals a crossover to an insulating, Anderson-localized state occurs. Besides establishing the origin of the very large magnetoresistance of bulk WTe$_2$, our results represent the first, complete validation of the classical theory for two-band electron-hole transport, and indicate that atomically thin WTe$_2$ layers remain gapless semimetals, from which we conclude that searching for a topological insulating state by straining monolayers is a challenging, but feasible experiment. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1510.04827v2-abstract-full').style.display = 'none'; document.getElementById('1510.04827v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 19 October, 2015; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 16 October, 2015; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2015. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Originally submitted version including supplementary information, in compliance with editorial guidelines. The final version will appear on Nature Communications soon</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1404.7691">arXiv:1404.7691</a> <span> [<a href="https://arxiv.org/pdf/1404.7691">pdf</a>, <a href="https://arxiv.org/ps/1404.7691">ps</a>, <a href="https://arxiv.org/format/1404.7691">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1063/1.4872002">10.1063/1.4872002 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Scanning photocurrent microscopy reveals electron-hole asymmetry in ionic liquid-gated WS2 transistors </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Ubrig%2C+N">Nicolas Ubrig</a>, <a href="/search/cond-mat?searchtype=author&query=Jo%2C+S">Sanghyun Jo</a>, <a href="/search/cond-mat?searchtype=author&query=Berger%2C+H">Helmuth Berger</a>, <a href="/search/cond-mat?searchtype=author&query=Morpurgo%2C+A+F">Alberto F. Morpurgo</a>, <a href="/search/cond-mat?searchtype=author&query=Kuzmenko%2C+A+B">Alexey B. Kuzmenko</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1404.7691v1-abstract-short" style="display: inline;"> We perform scanning photocurrent microscopy on WS2 ionic liquid-gated field effect transistors exhibiting high-quality ambipolar transport. By properly biasing the gate electrode we can invert the sign of the photocurrent showing that the minority photocarriers are either electrons or holes. Both in the electron- and the hole-doping regimes the photocurrent decays exponentially as a function of th… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1404.7691v1-abstract-full').style.display = 'inline'; document.getElementById('1404.7691v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1404.7691v1-abstract-full" style="display: none;"> We perform scanning photocurrent microscopy on WS2 ionic liquid-gated field effect transistors exhibiting high-quality ambipolar transport. By properly biasing the gate electrode we can invert the sign of the photocurrent showing that the minority photocarriers are either electrons or holes. Both in the electron- and the hole-doping regimes the photocurrent decays exponentially as a function of the distance between the illumination spot and the nearest contact, in agreement with a two-terminal Schottky-barrier device model. This allows us to compare the value and the doping dependence of the diffusion length of the minority electrons and holes on a same sample. Interestingly, the diffusion length of the minority carriers is several times larger in the hole accumulation regime than in the electron accumulation regime, pointing out an electron-hole asymmetry in WS2. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1404.7691v1-abstract-full').style.display = 'none'; document.getElementById('1404.7691v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 30 April, 2014; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 2014. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Appl. Phys. Lett. 104, 171112 (2014) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1403.7551">arXiv:1403.7551</a> <span> [<a href="https://arxiv.org/pdf/1403.7551">pdf</a>, <a href="https://arxiv.org/format/1403.7551">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1021/nl500171v">10.1021/nl500171v <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Mono- and Bilayer WS2 Light-Emitting Transistors </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Jo%2C+S">Sanghyun Jo</a>, <a href="/search/cond-mat?searchtype=author&query=Ubrig%2C+N">Nicolas Ubrig</a>, <a href="/search/cond-mat?searchtype=author&query=Berger%2C+H">Helmuth Berger</a>, <a href="/search/cond-mat?searchtype=author&query=Kuzmenko%2C+A+B">Alexey B. Kuzmenko</a>, <a href="/search/cond-mat?searchtype=author&query=Morpurgo%2C+A+F">Alberto F. Morpurgo</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1403.7551v1-abstract-short" style="display: inline;"> We have realized ambipolar ionic liquid gated field-effect transistors based on WS2 mono- and bilayers, and investigated their opto-electronic response. A thorough characterization of the transport properties demonstrates the high quality of these devices for both electron and hole accumulation, which enables the quantitative determination of the band gap (螖1L = 2.14 eV for monolayers and 螖2L = 1.… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1403.7551v1-abstract-full').style.display = 'inline'; document.getElementById('1403.7551v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1403.7551v1-abstract-full" style="display: none;"> We have realized ambipolar ionic liquid gated field-effect transistors based on WS2 mono- and bilayers, and investigated their opto-electronic response. A thorough characterization of the transport properties demonstrates the high quality of these devices for both electron and hole accumulation, which enables the quantitative determination of the band gap (螖1L = 2.14 eV for monolayers and 螖2L = 1.82 eV for bilayers). It also enables the operation of the transistors in the ambipolar injection regime with electrons and holes injected simultaneously at the two opposite contacts of the devices in which we observe light emission from the FET channel. A quantitative analysis of the spectral properties of the emitted light, together with a comparison with the band gap values obtained from transport, show the internal consistency of our results and allow a quantitative estimate of the excitonic binding energies to be made. Our results demonstrate the power of ionic liquid gating in combination with nanoelectronic systems, as well as the compatibility of this technique with optical measurements on semiconducting transition metal dichalcogenides. These findings further open the way to the investigation of the optical properties of these systems in a carrier density range much broader than that explored until now. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1403.7551v1-abstract-full').style.display = 'none'; document.getElementById('1403.7551v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 28 March, 2014; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2014. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">22 pages, 6 figures, Nano Letters (2014)</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Nano Letters 14, 2019 (2014) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1303.1634">arXiv:1303.1634</a> <span> [<a href="https://arxiv.org/pdf/1303.1634">pdf</a>, <a href="https://arxiv.org/ps/1303.1634">ps</a>, <a href="https://arxiv.org/format/1303.1634">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1364/OE.21.024736">10.1364/OE.21.024736 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Fabry-Perot enhanced Faraday rotation in graphene </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Ubrig%2C+N">Nicolas Ubrig</a>, <a href="/search/cond-mat?searchtype=author&query=Crassee%2C+I">Iris Crassee</a>, <a href="/search/cond-mat?searchtype=author&query=Levallois%2C+J">Julien Levallois</a>, <a href="/search/cond-mat?searchtype=author&query=Nedoliuk%2C+I+O">Ievgeniia O. Nedoliuk</a>, <a href="/search/cond-mat?searchtype=author&query=Fromm%2C+F">Felix Fromm</a>, <a href="/search/cond-mat?searchtype=author&query=Kaiser%2C+M">Michl Kaiser</a>, <a href="/search/cond-mat?searchtype=author&query=Seyller%2C+T">Thomas Seyller</a>, <a href="/search/cond-mat?searchtype=author&query=Kuzmenko%2C+A+B">Alexey B. Kuzmenko</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1303.1634v2-abstract-short" style="display: inline;"> We demonstrate that giant Faraday rotation in graphene in the terahertz range due to the cyclotron resonance is further increased by constructive Fabry-Perot interference in the supporting substrate. Simultaneously, an enhanced total transmission is achieved, making this effect doubly advantageous for graphene-based magneto-optical applications. As an example, we present far-infrared spectra of ep… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1303.1634v2-abstract-full').style.display = 'inline'; document.getElementById('1303.1634v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1303.1634v2-abstract-full" style="display: none;"> We demonstrate that giant Faraday rotation in graphene in the terahertz range due to the cyclotron resonance is further increased by constructive Fabry-Perot interference in the supporting substrate. Simultaneously, an enhanced total transmission is achieved, making this effect doubly advantageous for graphene-based magneto-optical applications. As an example, we present far-infrared spectra of epitaxial multilayer graphene grown on the C-face of 6H-SiC, where the interference fringes are spectrally resolved and a Faraday rotation up to 0.15 radians (9掳) is attained. Further, we discuss and compare other ways to increase the Faraday rotation using the principle of an optical cavity. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1303.1634v2-abstract-full').style.display = 'none'; document.getElementById('1303.1634v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 12 October, 2013; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 7 March, 2013; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2013. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Optics Express, Vol. 21, Issue 21, pp. 24736-24741 (2013) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1209.0318">arXiv:1209.0318</a> <span> [<a href="https://arxiv.org/pdf/1209.0318">pdf</a>, <a href="https://arxiv.org/ps/1209.0318">ps</a>, <a href="https://arxiv.org/format/1209.0318">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1209/0295-5075/100/58003">10.1209/0295-5075/100/58003 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Infrared spectroscopy of hole doped ABA-stacked trilayer graphene </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Ubrig%2C+N">N. Ubrig</a>, <a href="/search/cond-mat?searchtype=author&query=Blake%2C+P">P. Blake</a>, <a href="/search/cond-mat?searchtype=author&query=van+der+Marel%2C+D">D. van der Marel</a>, <a href="/search/cond-mat?searchtype=author&query=Kuzmenko%2C+A+B">A. B. Kuzmenko</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1209.0318v2-abstract-short" style="display: inline;"> Using infrared spectroscopy, we investigate bottom gated ABA-stacked trilayer graphene subject to an additional environment-induced p-type doping. We find that the Slonczewski-Weiss-McClure tight-binding model and the Kubo formula reproduce the gate voltage-modulated reflectivity spectra very accurately. This allows us to determine the charge densities and the potentials of the 蟺-band electrons on… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1209.0318v2-abstract-full').style.display = 'inline'; document.getElementById('1209.0318v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1209.0318v2-abstract-full" style="display: none;"> Using infrared spectroscopy, we investigate bottom gated ABA-stacked trilayer graphene subject to an additional environment-induced p-type doping. We find that the Slonczewski-Weiss-McClure tight-binding model and the Kubo formula reproduce the gate voltage-modulated reflectivity spectra very accurately. This allows us to determine the charge densities and the potentials of the 蟺-band electrons on all graphene layers separately and to extract the interlayer permittivity due to higher energy bands. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1209.0318v2-abstract-full').style.display = 'none'; document.getElementById('1209.0318v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 23 December, 2012; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 3 September, 2012; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2012. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">6 pages, 6 figures Corrected sign of fig 3 and visibilty of fig 6</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> EPL 100 (2012) 58003 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1102.2756">arXiv:1102.2756</a> <span> [<a href="https://arxiv.org/pdf/1102.2756">pdf</a>, <a href="https://arxiv.org/ps/1102.2756">ps</a>, <a href="https://arxiv.org/format/1102.2756">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Other Condensed Matter">cond-mat.other</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevB.83.073401">10.1103/PhysRevB.83.073401 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> High field magneto-transmission investigation of natural graphite </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Ubrig%2C+N">N. Ubrig</a>, <a href="/search/cond-mat?searchtype=author&query=Plochocka%2C+P">P. Plochocka</a>, <a href="/search/cond-mat?searchtype=author&query=Kossacki%2C+P">P. Kossacki</a>, <a href="/search/cond-mat?searchtype=author&query=Orlita%2C+M">M. Orlita</a>, <a href="/search/cond-mat?searchtype=author&query=Maude%2C+D+K">D. K. Maude</a>, <a href="/search/cond-mat?searchtype=author&query=Portugall%2C+O">O. Portugall</a>, <a href="/search/cond-mat?searchtype=author&query=Rikken%2C+G+L+J+A">G. L. J. A. Rikken</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1102.2756v1-abstract-short" style="display: inline;"> Magneto-transmission measurements in magnetic fields in the range B=20-60T have been performed to probe the H and K-point Landau level transitions in natural graphite. At the H-point, two series of transitions, whose energy evolves as $\sqrt{B}$ are observed. A reduced Slonczewski, Weiss and McClure (SWM) model with only two parameters to describe the intra-layer (gamma0) and inter-layer (gamma1)… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1102.2756v1-abstract-full').style.display = 'inline'; document.getElementById('1102.2756v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1102.2756v1-abstract-full" style="display: none;"> Magneto-transmission measurements in magnetic fields in the range B=20-60T have been performed to probe the H and K-point Landau level transitions in natural graphite. At the H-point, two series of transitions, whose energy evolves as $\sqrt{B}$ are observed. A reduced Slonczewski, Weiss and McClure (SWM) model with only two parameters to describe the intra-layer (gamma0) and inter-layer (gamma1) coupling correctly describes all observed transitions. Polarization resolved measurements confirm that the observed apparent splitting of the H-point transitions at high magnetic field cannot be attributed to an asymmetry of the Dirac cone. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1102.2756v1-abstract-full').style.display = 'none'; document.getElementById('1102.2756v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 14 February, 2011; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2011. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">5 pages, 3 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Physical Review B 83, 073401 (2011) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/0802.3203">arXiv:0802.3203</a> <span> [<a href="https://arxiv.org/pdf/0802.3203">pdf</a>, <a href="https://arxiv.org/ps/0802.3203">ps</a>, <a href="https://arxiv.org/format/0802.3203">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Materials Science">cond-mat.mtrl-sci</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1103/PhysRevB.78.081402">10.1103/PhysRevB.78.081402 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Magneto-spectroscopy of Highly-Aligned Carbon Nanotubes: Identifying the Role of Threading Magnetic Flux </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Shaver%2C+J">J. Shaver</a>, <a href="/search/cond-mat?searchtype=author&query=Crooker%2C+S+A">S. A. Crooker</a>, <a href="/search/cond-mat?searchtype=author&query=Fagan%2C+J+A">J. A. Fagan</a>, <a href="/search/cond-mat?searchtype=author&query=Hobbie%2C+E+K">E. K. Hobbie</a>, <a href="/search/cond-mat?searchtype=author&query=Ubrig%2C+N">N. Ubrig</a>, <a href="/search/cond-mat?searchtype=author&query=Portugall%2C+O">O. Portugall</a>, <a href="/search/cond-mat?searchtype=author&query=Perebeinos%2C+V">V. Perebeinos</a>, <a href="/search/cond-mat?searchtype=author&query=Avouris%2C+P">Ph. Avouris</a>, <a href="/search/cond-mat?searchtype=author&query=Kono%2C+J">J. Kono</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="0802.3203v1-abstract-short" style="display: inline;"> We have investigated excitons in highly-aligned single-walled carbon nanotubes (SWCNTs) through optical spectroscopy at low temperature (1.5 K) and high magnetic fields ($\textbf{\textit{B}}$) up to 55 T. SWCNT/polyacrylic acid films were stretched, giving SWCNTs that are highly aligned along the direction of stretch ($\hat{n}$). Utilizing two well-defined measurement geometries,… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0802.3203v1-abstract-full').style.display = 'inline'; document.getElementById('0802.3203v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="0802.3203v1-abstract-full" style="display: none;"> We have investigated excitons in highly-aligned single-walled carbon nanotubes (SWCNTs) through optical spectroscopy at low temperature (1.5 K) and high magnetic fields ($\textbf{\textit{B}}$) up to 55 T. SWCNT/polyacrylic acid films were stretched, giving SWCNTs that are highly aligned along the direction of stretch ($\hat{n}$). Utilizing two well-defined measurement geometries, $\hat{n}\parallel\textbf{\textit{B}}$ and $\hat{n}\perp\textbf{\textit{B}}$, we provide unambiguous evidence that the photoluminescence energy and intensity are only sensitive to the $\textbf{\textit{B}}$-component parallel to the tube axis. A theoretical model of one-dimensional magneto-excitons, based on exchange-split `bright' and `dark' exciton bands with Aharonov-Bohm-phase-dependent energies, masses, and oscillator strengths, successfully reproduces our observations and allows determination of the splitting between the two bands as $\sim4.8$ meV for (6,5) SWCNTs. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0802.3203v1-abstract-full').style.display = 'none'; document.getElementById('0802.3203v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 21 February, 2008; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2008. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">4 pages, 4 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Physical Review B 78, 081402(R) (2008) </p> </li> </ol> <div class="is-hidden-tablet">  <span class="help" style="display: inline-block;"><a href="https://github.com/arXiv/arxiv-search/releases">Search v0.5.6 released 2020-02-24</a>  </span> </div> </div> </main> <footer> <div class="columns is-desktop" role="navigation" aria-label="Secondary">  <div class="column"> <div class="columns"> <div class="column"> <ul class="nav-spaced"> <li><a href="https://info.arxiv.org/about">About</a></li> <li><a href="https://info.arxiv.org/help">Help</a></li> </ul> </div> <div class="column"> <ul class="nav-spaced"> <li> <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 512 512" class="icon filter-black" role="presentation"><title>contact arXiv</title><desc>Click here to contact arXiv</desc><path d="M502.3 190.8c3.9-3.1 9.7-.2 9.7 4.7V400c0 26.5-21.5 48-48 48H48c-26.5 0-48-21.5-48-48V195.6c0-5 5.7-7.8 9.7-4.7 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