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</div> <div class="control"> <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/2410.16269">arXiv:2410.16269</a> <span> [<a href="https://arxiv.org/pdf/2410.16269">pdf</a>, <a href="https://arxiv.org/format/2410.16269">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> </div> </div> <p class="title is-5 mathjax"> Imaging supermoire relaxation and conductive domain walls in helical trilayer graphene </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Hoke%2C+J+C">Jesse C. Hoke</a>, <a href="/search/cond-mat?searchtype=author&query=Li%2C+Y">Yifan Li</a>, <a href="/search/cond-mat?searchtype=author&query=Hu%2C+Y">Yuwen Hu</a>, <a href="/search/cond-mat?searchtype=author&query=May-Mann%2C+J">Julian May-Mann</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=Devakul%2C+T">Trithep Devakul</a>, <a href="/search/cond-mat?searchtype=author&query=Feldman%2C+B+E">Benjamin E. Feldman</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="2410.16269v1-abstract-short" style="display: inline;"> In twisted van der Waals materials, local atomic relaxation can significantly alter the underlying electronic structure and properties. Characterizing the lattice reconstruction and the impact of strain is essential to better understand and harness the resulting emergent electronic states. Here, we use a scanning single-electron transistor to image spatial modulations in the electronic structure o… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2410.16269v1-abstract-full').style.display = 'inline'; document.getElementById('2410.16269v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2410.16269v1-abstract-full" style="display: none;"> In twisted van der Waals materials, local atomic relaxation can significantly alter the underlying electronic structure and properties. Characterizing the lattice reconstruction and the impact of strain is essential to better understand and harness the resulting emergent electronic states. Here, we use a scanning single-electron transistor to image spatial modulations in the electronic structure of helical trilayer graphene, demonstrating relaxation into a superstructure of large domains with uniform moire periodicity. We further show that the supermoire domain size is enhanced by strain and can even be altered in subsequent measurements of the same device, while nevertheless maintaining the same local electronic properties within each domain. Finally, we observe higher conductance at the boundaries between domains, consistent with the prediction that they host counter-propagating topological edge modes. Our work confirms that lattice relaxation can produce moire-periodic order in twisted multilayers, demonstrates strain-engineering as a viable path for designing topological networks at the supermoire scale, and paves the way to direct imaging of correlation-driven topological phases and boundary modes. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2410.16269v1-abstract-full').style.display = 'none'; document.getElementById('2410.16269v1-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 October, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2024. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2401.04373">arXiv:2401.04373</a> <span> [<a href="https://arxiv.org/pdf/2401.04373">pdf</a>, <a href="https://arxiv.org/format/2401.04373">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/10.1007/s10909-023-03035-4">10.1007/s10909-023-03035-4 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Characterization of two fast-turnaround dry dilution refrigerators for scanning probe microscopy </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Barber%2C+M+E">Mark E. Barber</a>, <a href="/search/cond-mat?searchtype=author&query=Li%2C+Y">Yifan Li</a>, <a href="/search/cond-mat?searchtype=author&query=Gibson%2C+J">Jared Gibson</a>, <a href="/search/cond-mat?searchtype=author&query=Yu%2C+J">Jiachen Yu</a>, <a href="/search/cond-mat?searchtype=author&query=Jiang%2C+Z">Zhanzhi Jiang</a>, <a href="/search/cond-mat?searchtype=author&query=Hu%2C+Y">Yuwen Hu</a>, <a href="/search/cond-mat?searchtype=author&query=Ji%2C+Z">Zhurun Ji</a>, <a href="/search/cond-mat?searchtype=author&query=Nandi%2C+N">Nabhanila Nandi</a>, <a href="/search/cond-mat?searchtype=author&query=Hoke%2C+J+C">Jesse C. Hoke</a>, <a href="/search/cond-mat?searchtype=author&query=Horn%2C+L+B">Logan Bishop-Van Horn</a>, <a href="/search/cond-mat?searchtype=author&query=Arias%2C+G+R">Gilbert R. Arias</a>, <a href="/search/cond-mat?searchtype=author&query=Van+Harlingen%2C+D+J">Dale J. Van Harlingen</a>, <a href="/search/cond-mat?searchtype=author&query=Moler%2C+K+A">Kathryn A. Moler</a>, <a href="/search/cond-mat?searchtype=author&query=Shen%2C+Z">Zhi-Xun Shen</a>, <a href="/search/cond-mat?searchtype=author&query=Kou%2C+A">Angela Kou</a>, <a href="/search/cond-mat?searchtype=author&query=Feldman%2C+B+E">Benjamin E. Feldman</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="2401.04373v1-abstract-short" style="display: inline;"> Low-temperature scanning probe microscopes (SPMs) are critical for the study of quantum materials and quantum information science. Due to the rising costs of helium, cryogen-free cryostats have become increasingly desirable. However, they typically suffer from comparatively worse vibrations than cryogen-based systems, necessitating the understanding and mitigation of vibrations for SPM application… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2401.04373v1-abstract-full').style.display = 'inline'; document.getElementById('2401.04373v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2401.04373v1-abstract-full" style="display: none;"> Low-temperature scanning probe microscopes (SPMs) are critical for the study of quantum materials and quantum information science. Due to the rising costs of helium, cryogen-free cryostats have become increasingly desirable. However, they typically suffer from comparatively worse vibrations than cryogen-based systems, necessitating the understanding and mitigation of vibrations for SPM applications. Here we demonstrate the construction of two cryogen-free dilution refrigerator SPMs with minimal modifications to the factory default and we systematically characterize their vibrational performance. We measure the absolute vibrations at the microscope stage with geophones, and use both microwave impedance microscopy and a scanning single electron transistor to independently measure tip-sample vibrations. Additionally, we implement customized filtering and thermal anchoring schemes, and characterize the cooling power at the scanning stage and the tip electron temperature. This work serves as a reference to researchers interested in cryogen-free SPMs, as such characterization is not standardized in the literature or available from manufacturers. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2401.04373v1-abstract-full').style.display = 'none'; document.getElementById('2401.04373v1-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> 9 January, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2024. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2401.01486">arXiv:2401.01486</a> <span> [<a href="https://arxiv.org/pdf/2401.01486">pdf</a>, <a href="https://arxiv.org/format/2401.01486">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/PhysRevX.14.031018">10.1103/PhysRevX.14.031018 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Anomalous Landau level gaps near magnetic transitions in monolayer WSe$_2$ </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Foutty%2C+B+A">Benjamin A. Foutty</a>, <a href="/search/cond-mat?searchtype=author&query=Calvera%2C+V">Vladimir Calvera</a>, <a href="/search/cond-mat?searchtype=author&query=Han%2C+Z">Zhaoyu Han</a>, <a href="/search/cond-mat?searchtype=author&query=Kometter%2C+C+R">Carlos R. Kometter</a>, <a href="/search/cond-mat?searchtype=author&query=Liu%2C+S">Song Liu</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=Hone%2C+J+C">James C. Hone</a>, <a href="/search/cond-mat?searchtype=author&query=Kivelson%2C+S+A">Steven A. Kivelson</a>, <a href="/search/cond-mat?searchtype=author&query=Feldman%2C+B+E">Benjamin E. Feldman</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="2401.01486v1-abstract-short" style="display: inline;"> First-order phase transitions produce abrupt changes to the character of both ground and excited electronic states. Here we conduct electronic compressibility measurements to map the spin phase diagram and Landau level (LL) energies of monolayer WSe$_2$ in a magnetic field. We resolve a sequence of first-order phase transitions between completely spin-polarized LLs and states with LLs of both spin… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2401.01486v1-abstract-full').style.display = 'inline'; document.getElementById('2401.01486v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2401.01486v1-abstract-full" style="display: none;"> First-order phase transitions produce abrupt changes to the character of both ground and excited electronic states. Here we conduct electronic compressibility measurements to map the spin phase diagram and Landau level (LL) energies of monolayer WSe$_2$ in a magnetic field. We resolve a sequence of first-order phase transitions between completely spin-polarized LLs and states with LLs of both spins. Unexpectedly, the LL gaps are roughly constant over a wide range of magnetic fields below the transitions, which we show reflects a preference for opposite spin excitations of the spin-polarized ground state. These transitions also extend into compressible regimes, with a sawtooth boundary between full and partial spin polarization. We link these observations to the important influence of LL filling on the exchange energy beyond a smooth density-dependent contribution. Our results show that WSe$_2$ realizes a unique hierarchy of energy scales where such effects induce re-entrant magnetic phase transitions tuned by density and magnetic field. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2401.01486v1-abstract-full').style.display = 'none'; document.getElementById('2401.01486v1-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 January, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. X 14, 031018 (2024) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2311.04211">arXiv:2311.04211</a> <span> [<a href="https://arxiv.org/pdf/2311.04211">pdf</a>, <a href="https://arxiv.org/format/2311.04211">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"> Harnessing excitons at the nanoscale -- photoelectrical platform for quantitative sensing and imaging </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Ji%2C+Z">Zhurun Ji</a>, <a href="/search/cond-mat?searchtype=author&query=Barber%2C+M+E">Mark E. Barber</a>, <a href="/search/cond-mat?searchtype=author&query=Zhu%2C+Z">Ziyan Zhu</a>, <a href="/search/cond-mat?searchtype=author&query=Kometter%2C+C+R">Carlos R. Kometter</a>, <a href="/search/cond-mat?searchtype=author&query=Yu%2C+J">Jiachen Yu</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=Liu%2C+M">Mengkun Liu</a>, <a href="/search/cond-mat?searchtype=author&query=Devereaux%2C+T+P">Thomas P. Devereaux</a>, <a href="/search/cond-mat?searchtype=author&query=Feldman%2C+B+E">Benjamin E. Feldman</a>, <a href="/search/cond-mat?searchtype=author&query=Shen%2C+Z">Zhixun Shen</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="2311.04211v3-abstract-short" style="display: inline;"> Excitons -- quasiparticles formed by the binding of an electron and a hole through electrostatic attraction -- hold promise in the fields of quantum light confinement and optoelectronic sensing. Atomically thin transition metal dichalcogenides (TMDs) provide a versatile platform for hosting and manipulating excitons, given their robust Coulomb interactions and exceptional sensitivity to dielectric… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2311.04211v3-abstract-full').style.display = 'inline'; document.getElementById('2311.04211v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2311.04211v3-abstract-full" style="display: none;"> Excitons -- quasiparticles formed by the binding of an electron and a hole through electrostatic attraction -- hold promise in the fields of quantum light confinement and optoelectronic sensing. Atomically thin transition metal dichalcogenides (TMDs) provide a versatile platform for hosting and manipulating excitons, given their robust Coulomb interactions and exceptional sensitivity to dielectric environments. In this study, we introduce a cryogenic scanning probe photoelectrical sensing platform, termed exciton-resonant microwave impedance microscopy (ER-MIM). ER-MIM enables ultra-sensitive probing of exciton polarons and their Rydberg states at the nanoscale. Utilizing this technique, we explore the interplay between excitons and material properties, including carrier density, in-plane electric field, and dielectric screening. Furthermore, we employ deep learning for automated data analysis and quantitative extraction of electrical information, unveiling the potential of exciton-assisted nano-electrometry. Our findings establish an invaluable sensing platform and readout mechanism, advancing our understanding of exciton excitations and their applications in the quantum realm. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2311.04211v3-abstract-full').style.display = 'none'; document.getElementById('2311.04211v3-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> 18 December, 2023; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 7 November, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2023. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2309.07876">arXiv:2309.07876</a> <span> [<a href="https://arxiv.org/pdf/2309.07876">pdf</a>, <a href="https://arxiv.org/format/2309.07876">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="Mesoscale and Nanoscale Physics">cond-mat.mes-hall</span> </div> </div> <p class="title is-5 mathjax"> Particle-hole asymmetric ferromagnetism and spin textures in the triangular Hubbard-Hofstadter model </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Ding%2C+J+K">Jixun K. Ding</a>, <a href="/search/cond-mat?searchtype=author&query=Yang%2C+L">Luhang Yang</a>, <a href="/search/cond-mat?searchtype=author&query=Wang%2C+W+O">Wen O. Wang</a>, <a href="/search/cond-mat?searchtype=author&query=Zhu%2C+Z">Ziyan Zhu</a>, <a href="/search/cond-mat?searchtype=author&query=Peng%2C+C">Cheng Peng</a>, <a href="/search/cond-mat?searchtype=author&query=Mai%2C+P">Peizhi Mai</a>, <a href="/search/cond-mat?searchtype=author&query=Huang%2C+E+W">Edwin W. Huang</a>, <a href="/search/cond-mat?searchtype=author&query=Moritz%2C+B">Brian Moritz</a>, <a href="/search/cond-mat?searchtype=author&query=Phillips%2C+P+W">Philip W. Phillips</a>, <a href="/search/cond-mat?searchtype=author&query=Feldman%2C+B+E">Benjamin E. Feldman</a>, <a href="/search/cond-mat?searchtype=author&query=Devereaux%2C+T+P">Thomas P. Devereaux</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="2309.07876v2-abstract-short" style="display: inline;"> In a lattice model subject to a perpendicular magnetic field, when the lattice constant is comparable to the magnetic length, one enters the "Hofstadter regime," where continuum Landau levels become fractal magnetic Bloch bands. Strong mixing between bands alters the nature of the resulting quantum phases compared to the continuum limit; lattice potential, magnetic field, and Coulomb interaction m… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2309.07876v2-abstract-full').style.display = 'inline'; document.getElementById('2309.07876v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2309.07876v2-abstract-full" style="display: none;"> In a lattice model subject to a perpendicular magnetic field, when the lattice constant is comparable to the magnetic length, one enters the "Hofstadter regime," where continuum Landau levels become fractal magnetic Bloch bands. Strong mixing between bands alters the nature of the resulting quantum phases compared to the continuum limit; lattice potential, magnetic field, and Coulomb interaction must be treated on equal footing. Using determinant quantum Monte Carlo (DQMC) and density matrix renormalization group (DMRG) techniques, we study this regime numerically in the context of the Hubbard-Hofstadter model on a triangular lattice. In the field-filling phase diagram, we find a broad wedge-shaped region of ferromagnetic ground states for filling factor $谓\leq 1$, bounded below by filling factor $谓= 1$ and bounded above by half-filling the lowest Hofstadter subband. We observe signatures of SU(2) quantum Hall ferromagnetism at filling factors $谓=1$ and $谓=3$. The phases near $谓=1$ are particle-hole asymmetric, and we observe a rapid decrease in ground state spin polarization consistent with the formation of skyrmions only on the electron doped side. At large fields, above the ferromagnetic wedge, we observe a low-spin metallic region with spin correlations peaked at small momenta. We argue that the phenomenology of this region likely results from exchange interaction mixing fractal Hofstadter subbands. The phase diagram derived beyond the continuum limit points to a rich landscape to explore interaction effects in magnetic Bloch bands. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2309.07876v2-abstract-full').style.display = 'none'; document.getElementById('2309.07876v2-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> 1 March, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 14 September, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 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">10+7 pages, 6+13 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/2309.06583">arXiv:2309.06583</a> <span> [<a href="https://arxiv.org/pdf/2309.06583">pdf</a>, <a href="https://arxiv.org/format/2309.06583">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> </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/s41467-024-48385-z">10.1038/s41467-024-48385-z <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Uncovering the spin ordering in magic-angle graphene via edge state equilibration </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Hoke%2C+J+C">Jesse C. Hoke</a>, <a href="/search/cond-mat?searchtype=author&query=Li%2C+Y">Yifan Li</a>, <a href="/search/cond-mat?searchtype=author&query=May-Mann%2C+J">Julian May-Mann</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=Bradlyn%2C+B">Barry Bradlyn</a>, <a href="/search/cond-mat?searchtype=author&query=Hughes%2C+T+L">Taylor L. Hughes</a>, <a href="/search/cond-mat?searchtype=author&query=Feldman%2C+B+E">Benjamin E. Feldman</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="2309.06583v2-abstract-short" style="display: inline;"> Determining the symmetry breaking order of correlated quantum phases is essential for understanding the microscopic interactions in their host systems. The flat bands in magic angle twisted bilayer graphene (MATBG) provide an especially rich arena to investigate such interaction-driven ground states, and while progress has been made in identifying the correlated insulators and their excitations at… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2309.06583v2-abstract-full').style.display = 'inline'; document.getElementById('2309.06583v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2309.06583v2-abstract-full" style="display: none;"> Determining the symmetry breaking order of correlated quantum phases is essential for understanding the microscopic interactions in their host systems. The flat bands in magic angle twisted bilayer graphene (MATBG) provide an especially rich arena to investigate such interaction-driven ground states, and while progress has been made in identifying the correlated insulators and their excitations at commensurate moire filling factors, the spin-valley polarizations of the topological states that emerge at high magnetic field remain unknown. Here we introduce a new technique based on twist-decoupled van der Waals layers that enables measurements of their electronic band structure and, by studying the backscattering between counter-propagating edge states, determination of relative spin polarization of the their edge modes. Applying this method to twist-decoupled MATBG and monolayer graphene, we find that the broken-symmetry quantum Hall states that extend from the charge neutrality point in MATBG are spin-unpolarized at even integer filling factors. The measurements also indicate that the correlated Chern insulator emerging from half filling of the flat valence band is spin-unpolarized, but suggest that its conduction band counterpart may be spin-polarized. Our results constrain models of spin-valley ordering in MATBG and establish a versatile approach to study the electronic properties of van der Waals systems. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2309.06583v2-abstract-full').style.display = 'none'; document.getElementById('2309.06583v2-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, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 12 September, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2023. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2304.09808">arXiv:2304.09808</a> <span> [<a href="https://arxiv.org/pdf/2304.09808">pdf</a>, <a href="https://arxiv.org/format/2304.09808">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> </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.adi4728">10.1126/science.adi4728 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Mapping twist-tuned multiband topology in bilayer WSe$_2$ </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Foutty%2C+B+A">Benjamin A. Foutty</a>, <a href="/search/cond-mat?searchtype=author&query=Kometter%2C+C+R">Carlos R. Kometter</a>, <a href="/search/cond-mat?searchtype=author&query=Devakul%2C+T">Trithep Devakul</a>, <a href="/search/cond-mat?searchtype=author&query=Reddy%2C+A+P">Aidan P. Reddy</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=Fu%2C+L">Liang Fu</a>, <a href="/search/cond-mat?searchtype=author&query=Feldman%2C+B+E">Benjamin E. Feldman</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="2304.09808v3-abstract-short" style="display: inline;"> Semiconductor moir茅 superlattices have been shown to host a wide array of interaction-driven ground states. However, twisted homobilayers have been difficult to study in the limit of large moir茅 wavelength, where interactions are most dominant. Here, we conduct local electronic compressibility measurements of twisted bilayer WSe$_2$ (tWSe$_2$) at small twist angles. We demonstrate multiple topolog… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2304.09808v3-abstract-full').style.display = 'inline'; document.getElementById('2304.09808v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2304.09808v3-abstract-full" style="display: none;"> Semiconductor moir茅 superlattices have been shown to host a wide array of interaction-driven ground states. However, twisted homobilayers have been difficult to study in the limit of large moir茅 wavelength, where interactions are most dominant. Here, we conduct local electronic compressibility measurements of twisted bilayer WSe$_2$ (tWSe$_2$) at small twist angles. We demonstrate multiple topological bands which host a series of Chern insulators at zero magnetic field near a 'magic angle' around $1.23^\circ$. Using a locally applied electric field, we induce a topological quantum phase transition at one hole per moir茅 unit cell. Our work establishes the topological phase diagram of a generalized Kane-Mele-Hubbard model in tWSe$_2$, demonstrating a tunable platform for strongly correlated topological phases. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2304.09808v3-abstract-full').style.display = 'none'; document.getElementById('2304.09808v3-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> 29 April, 2024; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 19 April, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 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">This is the author's version of the work. It is posted here by permission of the AAAS for personal use, not for redistribution. The definitive version was published in Science 384 (doi below)</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Science 384 (6693), 343-347 (2024) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2212.05068">arXiv:2212.05068</a> <span> [<a href="https://arxiv.org/pdf/2212.05068">pdf</a>, <a href="https://arxiv.org/format/2212.05068">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/s41567-023-02195-0">10.1038/s41567-023-02195-0 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Hofstadter states and reentrant charge order in a semiconductor moir茅 lattice </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Kometter%2C+C+R">Carlos R. Kometter</a>, <a href="/search/cond-mat?searchtype=author&query=Yu%2C+J">Jiachen Yu</a>, <a href="/search/cond-mat?searchtype=author&query=Devakul%2C+T">Trithep Devakul</a>, <a href="/search/cond-mat?searchtype=author&query=Reddy%2C+A+P">Aidan P. Reddy</a>, <a href="/search/cond-mat?searchtype=author&query=Zhang%2C+Y">Yang Zhang</a>, <a href="/search/cond-mat?searchtype=author&query=Foutty%2C+B+A">Benjamin A. Foutty</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=Fu%2C+L">Liang Fu</a>, <a href="/search/cond-mat?searchtype=author&query=Feldman%2C+B+E">Benjamin E. Feldman</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="2212.05068v1-abstract-short" style="display: inline;"> The emergence of moir茅 materials with flat bands provides a platform to systematically investigate and precisely control correlated electronic phases. Here, we report local electronic compressibility measurements of a twisted WSe$_2$/MoSe$_2$ heterobilayer which reveal a rich phase diagram of interpenetrating Hofstadter states and electron solids. We show that this reflects the presence of both fl… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2212.05068v1-abstract-full').style.display = 'inline'; document.getElementById('2212.05068v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2212.05068v1-abstract-full" style="display: none;"> The emergence of moir茅 materials with flat bands provides a platform to systematically investigate and precisely control correlated electronic phases. Here, we report local electronic compressibility measurements of a twisted WSe$_2$/MoSe$_2$ heterobilayer which reveal a rich phase diagram of interpenetrating Hofstadter states and electron solids. We show that this reflects the presence of both flat and dispersive moir茅 bands whose relative energies, and therefore occupations, are tuned by density and magnetic field. At low densities, competition between moir茅 bands leads to a transition from commensurate arrangements of singlets at doubly occupied sites to triplet configurations at high fields. Hofstadter states (i.e., Chern insulators) are generally favored at high densities as dispersive bands are populated, but are suppressed by an intervening region of reentrant charge-ordered states in which holes originating from multiple bands cooperatively crystallize. Our results reveal the key microscopic ingredients that favor distinct correlated ground states in semiconductor moir茅 systems, and they demonstrate an emergent lattice model system in which both interactions and band dispersion can be experimentally controlled. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2212.05068v1-abstract-full').style.display = 'none'; document.getElementById('2212.05068v1-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> 9 December, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 2022. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Nature Physics 19, 1861-1867 (2023) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2210.11486">arXiv:2210.11486</a> <span> [<a href="https://arxiv.org/pdf/2210.11486">pdf</a>, <a href="https://arxiv.org/format/2210.11486">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> </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/s41467-023-41465-6">10.1038/s41467-023-41465-6 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> 1/4 is the new 1/2 when topology is intertwined with Mottness </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Mai%2C+P">Peizhi Mai</a>, <a href="/search/cond-mat?searchtype=author&query=Zhao%2C+J">Jinchao Zhao</a>, <a href="/search/cond-mat?searchtype=author&query=Feldman%2C+B+E">Benjamin E. Feldman</a>, <a href="/search/cond-mat?searchtype=author&query=Phillips%2C+P+W">Philip W. Phillips</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="2210.11486v5-abstract-short" style="display: inline;"> In non-interacting systems, bands from non-trivial topology emerge strictly at half-filling and exhibit either the quantum anomalous Hall or spin Hall effects. Here we show using determinantal quantum Monte Carlo and an exactly solvable strongly interacting model that these topological states now shift to quarter filling. A topological Mott insulator is the underlying cause. The peak in the spin s… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2210.11486v5-abstract-full').style.display = 'inline'; document.getElementById('2210.11486v5-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2210.11486v5-abstract-full" style="display: none;"> In non-interacting systems, bands from non-trivial topology emerge strictly at half-filling and exhibit either the quantum anomalous Hall or spin Hall effects. Here we show using determinantal quantum Monte Carlo and an exactly solvable strongly interacting model that these topological states now shift to quarter filling. A topological Mott insulator is the underlying cause. The peak in the spin susceptibility is consistent with a possible ferromagnetic state at $T=0$. The onset of such magnetism would convert the quantum spin Hall to a quantum anomalous Hall effect. While such a symmetry-broken phase typically is accompanied by a gap, we find that the interaction strength must exceed a critical value for this to occur. Hence, we predict that topology can obtain in a gapless phase but only in the presence of interactions in dispersive bands. These results explain the recent quarter-filled quantum anomalous Hall effects seen in moire systems. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2210.11486v5-abstract-full').style.display = 'none'; document.getElementById('2210.11486v5-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> 5 September, 2023; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 20 October, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 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">Figure 4e,f added as well as a reference</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2207.01638">arXiv:2207.01638</a> <span> [<a href="https://arxiv.org/pdf/2207.01638">pdf</a>, <a href="https://arxiv.org/format/2207.01638">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> </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.5.013162">10.1103/PhysRevResearch.5.013162 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Topological Mott Insulator at Quarter Filling in the Interacting Haldane Model </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Mai%2C+P">Peizhi Mai</a>, <a href="/search/cond-mat?searchtype=author&query=Feldman%2C+B+E">Benjamin E. Feldman</a>, <a href="/search/cond-mat?searchtype=author&query=Phillips%2C+P+W">Philip W. Phillips</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="2207.01638v4-abstract-short" style="display: inline;"> While the recent advances in topology have led to a classification scheme for electronic bands described by the standard theory of metals, a similar scheme has not emerged for strongly correlated systems such as Mott insulators in which a partially filled band carries no current. By including interactions in the topologically non-trivial Haldane model, we show that a quarter-filled state emerges w… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2207.01638v4-abstract-full').style.display = 'inline'; document.getElementById('2207.01638v4-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2207.01638v4-abstract-full" style="display: none;"> While the recent advances in topology have led to a classification scheme for electronic bands described by the standard theory of metals, a similar scheme has not emerged for strongly correlated systems such as Mott insulators in which a partially filled band carries no current. By including interactions in the topologically non-trivial Haldane model, we show that a quarter-filled state emerges with a non-zero Chern number provided the interactions are sufficiently large. We first motivate this result on physical grounds and then by two methods: analytically by solving exactly a model in which interactions are local in momentum space and then numerically through the corresponding Hubbard model. All methods yield the same result: For sufficiently large interaction strengths, the quarter-filled Haldane model is a ferromagnetic topological Mott insulator with a Chern number of unity. Possible experimental realizations in cold-atom and solid state systems are discussed. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2207.01638v4-abstract-full').style.display = 'none'; document.getElementById('2207.01638v4-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, 2023; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 4 July, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> July 2022. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2206.11304">arXiv:2206.11304</a> <span> [<a href="https://arxiv.org/pdf/2206.11304">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> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Strongly Correlated Electrons">cond-mat.str-el</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/s41467-023-42275-6">10.1038/s41467-023-42275-6 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Spin skyrmion gaps as signatures of strong-coupling insulators in magic-angle twisted bilayer graphene </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Yu%2C+J">Jiachen Yu</a>, <a href="/search/cond-mat?searchtype=author&query=Foutty%2C+B+A">Benjamin A. Foutty</a>, <a href="/search/cond-mat?searchtype=author&query=Kwan%2C+Y+H">Yves H. Kwan</a>, <a href="/search/cond-mat?searchtype=author&query=Barber%2C+M+E">Mark E. Barber</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=Shen%2C+Z">Zhi-Xun Shen</a>, <a href="/search/cond-mat?searchtype=author&query=Parameswaran%2C+S+A">Siddharth A. Parameswaran</a>, <a href="/search/cond-mat?searchtype=author&query=Feldman%2C+B+E">Benjamin E. Feldman</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="2206.11304v2-abstract-short" style="display: inline;"> The flat electronic bands in magic-angle twisted bilayer graphene (MATBG) host a variety of correlated insulating ground states, many of which are predicted to support charged excitations with topologically non-trivial spin and/or valley skyrmion textures. However, it has remained challenging to experimentally address their ground state order and excitations, both because some of the proposed stat… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2206.11304v2-abstract-full').style.display = 'inline'; document.getElementById('2206.11304v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2206.11304v2-abstract-full" style="display: none;"> The flat electronic bands in magic-angle twisted bilayer graphene (MATBG) host a variety of correlated insulating ground states, many of which are predicted to support charged excitations with topologically non-trivial spin and/or valley skyrmion textures. However, it has remained challenging to experimentally address their ground state order and excitations, both because some of the proposed states do not couple directly to experimental probes, and because they are highly sensitive to spatial inhomogeneities in real samples. Here, using a scanning single-electron transistor, we observe thermodynamic gaps at even integer moir茅 filling factors at low magnetic fields. We find evidence of a field-tuned crossover from charged spin skyrmions to bare particle-like excitations, suggesting that the underlying ground state belongs to the manifold of strong-coupling insulators. From the spatial dependence of these states and the chemical potential variation within the flat bands, we infer a link between the stability of the correlated ground states and local twist angle and strain. Our work advances the microscopic understanding of the correlated insulators in MATBG and their unconventional excitations. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2206.11304v2-abstract-full').style.display = 'none'; document.getElementById('2206.11304v2-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> 10 November, 2023; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 22 June, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 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">Supplementary information available at https://www.nature.com/articles/s41467-023-42275-6</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2206.10631">arXiv:2206.10631</a> <span> [<a href="https://arxiv.org/pdf/2206.10631">pdf</a>, <a href="https://arxiv.org/format/2206.10631">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> </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/s41563-023-01534-z">10.1038/s41563-023-01534-z <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Tunable spin and valley excitations of correlated insulators in $螕$-valley moir茅 bands </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Foutty%2C+B+A">Benjamin A. Foutty</a>, <a href="/search/cond-mat?searchtype=author&query=Yu%2C+J">Jiachen Yu</a>, <a href="/search/cond-mat?searchtype=author&query=Devakul%2C+T">Trithep Devakul</a>, <a href="/search/cond-mat?searchtype=author&query=Kometter%2C+C+R">Carlos R. Kometter</a>, <a href="/search/cond-mat?searchtype=author&query=Zhang%2C+Y">Yang Zhang</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=Fu%2C+L">Liang Fu</a>, <a href="/search/cond-mat?searchtype=author&query=Feldman%2C+B+E">Benjamin E. Feldman</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="2206.10631v3-abstract-short" style="display: inline;"> Moir茅 superlattices formed from transition metal dichalcogenides (TMDs) have been shown to support a variety of quantum electronic phases that are highly tunable using applied electromagnetic fields. While the valley character of the low-energy states dramatically affects optoelectronic properties in the constituent TMDs, this degree of freedom has yet to be fully explored in moir茅 systems. Here,… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2206.10631v3-abstract-full').style.display = 'inline'; document.getElementById('2206.10631v3-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2206.10631v3-abstract-full" style="display: none;"> Moir茅 superlattices formed from transition metal dichalcogenides (TMDs) have been shown to support a variety of quantum electronic phases that are highly tunable using applied electromagnetic fields. While the valley character of the low-energy states dramatically affects optoelectronic properties in the constituent TMDs, this degree of freedom has yet to be fully explored in moir茅 systems. Here, we establish twisted double bilayer WSe$_2$ as an experimental platform to study electronic correlations within $螕$-valley moir茅 bands. Through a combination of local and global electronic compressibility measurements, we identify charge-ordered phases at multiple integer and fractional moir茅 band fillings $谓$. By measuring the magnetic field dependence of their energy gaps and the chemical potential upon doping, we reveal spin-polarized ground states with novel spin polaron quasiparticle excitations. In addition, an applied displacement field allows us to realize a new mechanism of metal-insulator transition at $谓= -1$ driven by tuning between $螕$- and $K$-valley moir茅 bands. Together, our results demonstrate control over both the spin and valley character of the correlated ground and excited states in this system. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2206.10631v3-abstract-full').style.display = 'none'; document.getElementById('2206.10631v3-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, 2023; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 21 June, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2022. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2205.08545">arXiv:2205.08545</a> <span> [<a href="https://arxiv.org/pdf/2205.08545">pdf</a>, <a href="https://arxiv.org/format/2205.08545">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> </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/s41535-023-00544-z">10.1038/s41535-023-00544-z <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Interaction-driven Spontaneous Ferromagnetic Insulating States with Odd Chern Numbers </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Mai%2C+P">Peizhi Mai</a>, <a href="/search/cond-mat?searchtype=author&query=Huang%2C+E+W">Edwin W. Huang</a>, <a href="/search/cond-mat?searchtype=author&query=Yu%2C+J">Jiachen Yu</a>, <a href="/search/cond-mat?searchtype=author&query=Feldman%2C+B+E">Benjamin E. Feldman</a>, <a href="/search/cond-mat?searchtype=author&query=Phillips%2C+P+W">Philip W. Phillips</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="2205.08545v2-abstract-short" style="display: inline;"> Motivated by recent experimental work on moir茅 systems in a strong magnetic field, we compute the compressibility as well as the spin correlations and Hofstadter spectrum of spinful electrons on a honeycomb lattice with Hubbard interactions using the determinantal quantum Monte Carlo method. While the interactions in general preserve quantum and anomalous Hall states, emergent features arise corre… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2205.08545v2-abstract-full').style.display = 'inline'; document.getElementById('2205.08545v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2205.08545v2-abstract-full" style="display: none;"> Motivated by recent experimental work on moir茅 systems in a strong magnetic field, we compute the compressibility as well as the spin correlations and Hofstadter spectrum of spinful electrons on a honeycomb lattice with Hubbard interactions using the determinantal quantum Monte Carlo method. While the interactions in general preserve quantum and anomalous Hall states, emergent features arise corresponding to an antiferromagnetic insulator at half-filling and other incompressible states following the Chern sequence $\pm (2N+1)$. These odd integer Chern states exhibit strong ferromagnetic correlations and arise spontaneously without any external mechanism for breaking the spin-rotation symmetry. Analogs of these magnetic states should be observable in general interacting quantum Hall systems. In addition, the interacting Hofstadter spectrum is qualitatively similar to the experimental data at intermediate values of the on-site interaction. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2205.08545v2-abstract-full').style.display = 'none'; document.getElementById('2205.08545v2-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> 20 February, 2023; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 17 May, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 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">8 pages, 5 figures and a supplement</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2108.00009">arXiv:2108.00009</a> <span> [<a href="https://arxiv.org/pdf/2108.00009">pdf</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="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/s41567-022-01589-w">10.1038/s41567-022-01589-w <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Correlated Hofstadter Spectrum and Flavor Phase Diagram in Magic Angle Graphene </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Yu%2C+J">Jiachen Yu</a>, <a href="/search/cond-mat?searchtype=author&query=Foutty%2C+B+A">Benjamin A. Foutty</a>, <a href="/search/cond-mat?searchtype=author&query=Han%2C+Z">Zhaoyu Han</a>, <a href="/search/cond-mat?searchtype=author&query=Barber%2C+M+E">Mark E. Barber</a>, <a href="/search/cond-mat?searchtype=author&query=Schattner%2C+Y">Yoni Schattner</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=Phillips%2C+P">Philip Phillips</a>, <a href="/search/cond-mat?searchtype=author&query=Shen%2C+Z">Zhi-Xun Shen</a>, <a href="/search/cond-mat?searchtype=author&query=Kivelson%2C+S+A">Steven A. Kivelson</a>, <a href="/search/cond-mat?searchtype=author&query=Feldman%2C+B+E">Benjamin E. Feldman</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="2108.00009v1-abstract-short" style="display: inline;"> In magic angle twisted bilayer graphene (MATBG), the moir茅 superlattice potential gives rise to narrow electronic bands1 which support a multitude of many-body quantum phases. Further richness arises in the presence of a perpendicular magnetic field, where the interplay between moir茅 and magnetic length scales leads to fractal Hofstadter subbands. In this strongly correlated Hofstadter platform, m… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2108.00009v1-abstract-full').style.display = 'inline'; document.getElementById('2108.00009v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2108.00009v1-abstract-full" style="display: none;"> In magic angle twisted bilayer graphene (MATBG), the moir茅 superlattice potential gives rise to narrow electronic bands1 which support a multitude of many-body quantum phases. Further richness arises in the presence of a perpendicular magnetic field, where the interplay between moir茅 and magnetic length scales leads to fractal Hofstadter subbands. In this strongly correlated Hofstadter platform, multiple experiments have identified gapped topological and correlated states, but little is known about the phase transitions between them in the intervening compressible regimes. Here, using a scanning single-electron transistor microscope to measure local electronic compressibility, we simultaneously unveil novel sequences of broken-symmetry Chern insulators (CIs) and resolve sharp phase transitions between competing states with different topological quantum numbers and spin/valley flavor occupations. Our measurements provide a complete experimental mapping of the energy spectrum and thermodynamic phase diagram of interacting Hofstadter subbands in MATBG. In addition, we observe full lifting of the degeneracy of the zeroth Landau levels (zLLs) together with level crossings, indicating moir茅 valley splitting. We propose a unified flavor polarization mechanism to understand the intricate interplay of topology, interactions, and symmetry breaking as a function of density and applied magnetic field in this system. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2108.00009v1-abstract-full').style.display = 'none'; document.getElementById('2108.00009v1-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 July, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> August 2021. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1902.02790">arXiv:1902.02790</a> <span> [<a href="https://arxiv.org/pdf/1902.02790">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/s41586-019-0913-0">10.1038/s41586-019-0913-0 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Interacting multi-channel topological boundary modes in a quantum Hall valley system </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Randeria%2C+M+T">Mallika T. Randeria</a>, <a href="/search/cond-mat?searchtype=author&query=Agarwal%2C+K">Kartiek Agarwal</a>, <a href="/search/cond-mat?searchtype=author&query=Feldman%2C+B+E">Benjamin E. Feldman</a>, <a href="/search/cond-mat?searchtype=author&query=Ding%2C+H">Hao Ding</a>, <a href="/search/cond-mat?searchtype=author&query=Ji%2C+H">Huiwen Ji</a>, <a href="/search/cond-mat?searchtype=author&query=Cava%2C+R+J">R. J. Cava</a>, <a href="/search/cond-mat?searchtype=author&query=Sondhi%2C+S+L">S. L. Sondhi</a>, <a href="/search/cond-mat?searchtype=author&query=Parameswaran%2C+S+A">Siddharth A. Parameswaran</a>, <a href="/search/cond-mat?searchtype=author&query=Yazdani%2C+A">Ali Yazdani</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="1902.02790v1-abstract-short" style="display: inline;"> Symmetry and topology play key roles in the identification of phases of matter and their properties. Both concepts are central to understanding quantum Hall ferromagnets (QHFMs), two-dimensional electronic phases with spontaneously broken spin or pseudospin symmetry whose wavefunctions also have topological properties. Domain walls between distinct broken symmetry QHFM phases are predicted to host… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1902.02790v1-abstract-full').style.display = 'inline'; document.getElementById('1902.02790v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1902.02790v1-abstract-full" style="display: none;"> Symmetry and topology play key roles in the identification of phases of matter and their properties. Both concepts are central to understanding quantum Hall ferromagnets (QHFMs), two-dimensional electronic phases with spontaneously broken spin or pseudospin symmetry whose wavefunctions also have topological properties. Domain walls between distinct broken symmetry QHFM phases are predicted to host gapless one-dimensional (1D) modes that emerge due to a topological change of the underlying electronic wavefunctions at such interfaces. Although a variety of QHFMs have been identified in different materials, probing interacting electronic modes at these domain walls has not yet been accomplished. Here we use a scanning tunneling microscope (STM) to directly visualize the spontaneous formation of boundary modes, within a sign-changing topological gap, at domain walls between different valley-polarized quantum Hall phases on the surface of bismuth. By changing the valley occupation and the corresponding number of modes at the domain wall, we can realize different regimes where the valley-polarized channels are either metallic or develop a spectroscopic gap. This behavior is a consequence of Coulomb interactions constrained by the symmetry-breaking valley flavor, which determines whether electrons in the topological modes can backscatter, making these channels a unique class of interacting Luttinger liquids. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1902.02790v1-abstract-full').style.display = 'none'; document.getElementById('1902.02790v1-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> 7 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">Journal ref:</span> Nature (2019) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1809.09616">arXiv:1809.09616</a> <span> [<a href="https://arxiv.org/pdf/1809.09616">pdf</a>, <a href="https://arxiv.org/format/1809.09616">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="Disordered Systems and Neural Networks">cond-mat.dis-nn</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/10.1088/1361-648X/ab0636">10.1088/1361-648X/ab0636 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Quantum Hall Valley Nematics </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Parameswaran%2C+S+A">S. A. Parameswaran</a>, <a href="/search/cond-mat?searchtype=author&query=Feldman%2C+B+E">B. E. Feldman</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="1809.09616v1-abstract-short" style="display: inline;"> Two-dimensional electron gases in strong magnetic fields provide a canonical platform for realizing a variety of electronic ordering phenomena. Here we review the physics of one intriguing class of interaction-driven quantum Hall states: quantum Hall valley nematics. These phases of matter emerge when the formation of a topologically insulating quantum Hall state is accompanied by the spontaneous… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1809.09616v1-abstract-full').style.display = 'inline'; document.getElementById('1809.09616v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1809.09616v1-abstract-full" style="display: none;"> Two-dimensional electron gases in strong magnetic fields provide a canonical platform for realizing a variety of electronic ordering phenomena. Here we review the physics of one intriguing class of interaction-driven quantum Hall states: quantum Hall valley nematics. These phases of matter emerge when the formation of a topologically insulating quantum Hall state is accompanied by the spontaneous breaking of a point-group symmetry that combines a spatial rotation with a permutation of valley indices. The resulting orientational order is particularly sensitive to quenched disorder, while quantum Hall physics links charge conduction to topological defects. We discuss how these combine to yield a rich phase structure, and their implications for transport and spectroscopy measurements. In parallel, we discuss relevant experimental systems. We close with an outlook on future directions. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1809.09616v1-abstract-full').style.display = 'none'; document.getElementById('1809.09616v1-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 September, 2018; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 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">28 pages, 5 figures. Invited review article; comments welcome</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> J. Phys.: Condens. Matter 31 273001 (2019) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1805.04533">arXiv:1805.04533</a> <span> [<a href="https://arxiv.org/pdf/1805.04533">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/s41567-018-0148-2">10.1038/s41567-018-0148-2 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Ferroelectric quantum Hall phase revealed by visualizing Landau level wavefunction interference </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Randeria%2C+M+T">Mallika T. Randeria</a>, <a href="/search/cond-mat?searchtype=author&query=Feldman%2C+B+E">Benjamin E. Feldman</a>, <a href="/search/cond-mat?searchtype=author&query=Wu%2C+F">Fengcheng Wu</a>, <a href="/search/cond-mat?searchtype=author&query=Ding%2C+H">Hao Ding</a>, <a href="/search/cond-mat?searchtype=author&query=Gyenis%2C+A">Andras Gyenis</a>, <a href="/search/cond-mat?searchtype=author&query=Ji%2C+H">Huiwen Ji</a>, <a href="/search/cond-mat?searchtype=author&query=Cava%2C+R+J">R. J. Cava</a>, <a href="/search/cond-mat?searchtype=author&query=MacDonald%2C+A+H">Allan H. MacDonald</a>, <a href="/search/cond-mat?searchtype=author&query=Yazdani%2C+A">Ali Yazdani</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="1805.04533v1-abstract-short" style="display: inline;"> Novel broken symmetry states can spontaneously form due to Coulomb interactions in electronic systems with multiple internal degrees of freedom. Multi-valley materials offer an especially rich setting for the emergence of such states, which have potential electronic and optical applications. To date, identification of these broken symmetry phases has mostly relied on the examination of macroscopic… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1805.04533v1-abstract-full').style.display = 'inline'; document.getElementById('1805.04533v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1805.04533v1-abstract-full" style="display: none;"> Novel broken symmetry states can spontaneously form due to Coulomb interactions in electronic systems with multiple internal degrees of freedom. Multi-valley materials offer an especially rich setting for the emergence of such states, which have potential electronic and optical applications. To date, identification of these broken symmetry phases has mostly relied on the examination of macroscopic transport or optical properties. Here we demonstrate a powerful direct approach by visualizing the wave functions of bismuth surface states with a scanning tunneling microscope. Strong spin-orbit coupling on the surface of bismuth leads to six degenerate teardrop-shaped hole pockets. Our spectroscopic measurements reveal that this degeneracy is fully lifted at high magnetic field as a result of exchange interactions, and we are able to determine the nature of valley ordering by imaging the broken symmetry Landau level (LL) wave functions. The remarkable spatial features of singly degenerate LL wave functions near isolated defects contain unique signatures of interference between spin-textured valleys, which identify the electronic ground state as a quantum Hall ferroelectric. Our observations confirm the recent prediction that interactions in strongly anisotropic valley systems favor the occupation of a single valley, giving rise to emergent ferroelectricity in the surface state of bismuth. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1805.04533v1-abstract-full').style.display = 'none'; document.getElementById('1805.04533v1-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> 11 May, 2018; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 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">Accepted to Nature Physics, available through Advance Online Publication</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1802.02711">arXiv:1802.02711</a> <span> [<a href="https://arxiv.org/pdf/1802.02711">pdf</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> </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/s41467-018-02841-9">10.1038/s41467-018-02841-9 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Visualizing Heavy Fermion Confinement and Pauli-Limited Superconductivity in Layered CeCoIn5 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Gyenis%2C+A">Andr谩s Gyenis</a>, <a href="/search/cond-mat?searchtype=author&query=Feldman%2C+B+E">Benjamin E. Feldman</a>, <a href="/search/cond-mat?searchtype=author&query=Randeria%2C+M+T">Mallika T. Randeria</a>, <a href="/search/cond-mat?searchtype=author&query=Peterson%2C+G+A">Gabriel A. Peterson</a>, <a href="/search/cond-mat?searchtype=author&query=Bauer%2C+E+D">Eric D. Bauer</a>, <a href="/search/cond-mat?searchtype=author&query=Aynajian%2C+P">Pegor Aynajian</a>, <a href="/search/cond-mat?searchtype=author&query=Yazdani%2C+A">Ali Yazdani</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="1802.02711v1-abstract-short" style="display: inline;"> Layered material structures play a key role in enhancing electron-electron interactions to create correlated metallic phases that can transform into unconventional superconducting states. The quasi-two-dimensional electronic properties of such compounds are often inferred indirectly through examination of their bulk properties. Here we use scanning tunneling microscopy and spectroscopy to directly… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1802.02711v1-abstract-full').style.display = 'inline'; document.getElementById('1802.02711v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1802.02711v1-abstract-full" style="display: none;"> Layered material structures play a key role in enhancing electron-electron interactions to create correlated metallic phases that can transform into unconventional superconducting states. The quasi-two-dimensional electronic properties of such compounds are often inferred indirectly through examination of their bulk properties. Here we use scanning tunneling microscopy and spectroscopy to directly probe in cross section the quasi-two-dimensional correlated electronic states of the heavy fermion superconductor CeCoIn5. Our measurements reveal the strong confined nature of heavy quasi-particles, anisotropy of tunneling characteristics, and layer-by-layer modulated behavior of the precursor pseudogap gap phase in this compound. Examining the interlayer coupled superconducting state at low temperatures, we find that the orientation of line defects relative to the d-wave order parameter determines whether in-gap states form due to scattering. Spectroscopic imaging of the anisotropic magnetic vortex cores directly characterizes the short interlayer superconducting coherence length and shows an electronic phase separation near the upper critical in-plane magnetic field, consistent with a Pauli-limited first-order phase transition into a pseudogap phase. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1802.02711v1-abstract-full').style.display = 'none'; document.getElementById('1802.02711v1-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> 7 February, 2018; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2018. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Nature Communications 9, 549 (2018) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1611.02707">arXiv:1611.02707</a> <span> [<a href="https://arxiv.org/pdf/1611.02707">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/nphys3947">10.1038/nphys3947 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> High-resolution studies of the Majorana atomic chain platform </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Feldman%2C+B+E">Benjamin E. Feldman</a>, <a href="/search/cond-mat?searchtype=author&query=Randeria%2C+M+T">Mallika T. Randeria</a>, <a href="/search/cond-mat?searchtype=author&query=Li%2C+J">Jian Li</a>, <a href="/search/cond-mat?searchtype=author&query=Jeon%2C+S">Sangjun Jeon</a>, <a href="/search/cond-mat?searchtype=author&query=Xie%2C+Y">Yonglong Xie</a>, <a href="/search/cond-mat?searchtype=author&query=Wang%2C+Z">Zhijun Wang</a>, <a href="/search/cond-mat?searchtype=author&query=Drozdov%2C+I+K">Ilya K. Drozdov</a>, <a href="/search/cond-mat?searchtype=author&query=Bernevig%2C+B+A">B. Andrei Bernevig</a>, <a href="/search/cond-mat?searchtype=author&query=Yazdani%2C+A">Ali Yazdani</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="1611.02707v1-abstract-short" style="display: inline;"> Ordered assemblies of magnetic atoms on the surface of conventional superconductors can be used to engineer topological superconducting phases and realize Majorana fermion quasiparticles (MQPs) in a condensed matter setting. Recent experiments have shown that chains of Fe atoms on Pb generically have the required electronic characteristics to form a 1D topological superconductor and have revealed… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1611.02707v1-abstract-full').style.display = 'inline'; document.getElementById('1611.02707v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1611.02707v1-abstract-full" style="display: none;"> Ordered assemblies of magnetic atoms on the surface of conventional superconductors can be used to engineer topological superconducting phases and realize Majorana fermion quasiparticles (MQPs) in a condensed matter setting. Recent experiments have shown that chains of Fe atoms on Pb generically have the required electronic characteristics to form a 1D topological superconductor and have revealed spatially resolved signatures of localized MQPs at the ends of such chains. Here we report higher resolution measurements of the same atomic chain system performed using a dilution refrigerator scanning tunneling microscope (STM). With significantly better energy resolution than previous studies, we show that the zero bias peak (ZBP) in Fe chains has no detectable splitting from hybridization with other states. The measurements also reveal that the ZBP exhibits a distinctive 'double eye' spatial pattern on nanometer length scales. Theoretically we show that this is a general consequence of STM measurements of MQPs with substantial spectral weight in the superconducting substrate, a conclusion further supported by measurements of Pb overlayers deposited on top of the Fe chains. Finally, we report experiments performed with superconducting tips in search of the particle-hole symmetric MQP signature expected in such measurements. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1611.02707v1-abstract-full').style.display = 'none'; document.getElementById('1611.02707v1-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 November, 2016; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 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">Accepted to Nature Physics; available through Advance online publication</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1610.07613">arXiv:1610.07613</a> <span> [<a href="https://arxiv.org/pdf/1610.07613">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/10.1126/science.aag1715">10.1126/science.aag1715 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Observation of a Nematic Quantum Hall Liquid on the Surface of Bismuth </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Feldman%2C+B+E">Benjamin E. Feldman</a>, <a href="/search/cond-mat?searchtype=author&query=Randeria%2C+M+T">Mallika T. Randeria</a>, <a href="/search/cond-mat?searchtype=author&query=Gyenis%2C+A">Andr谩s Gyenis</a>, <a href="/search/cond-mat?searchtype=author&query=Wu%2C+F">Fengcheng Wu</a>, <a href="/search/cond-mat?searchtype=author&query=Ji%2C+H">Huiwen Ji</a>, <a href="/search/cond-mat?searchtype=author&query=Cava%2C+R+J">R. J. Cava</a>, <a href="/search/cond-mat?searchtype=author&query=MacDonald%2C+A+H">Allan H. MacDonald</a>, <a href="/search/cond-mat?searchtype=author&query=Yazdani%2C+A">Ali Yazdani</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="1610.07613v1-abstract-short" style="display: inline;"> Nematic quantum fluids with wavefunctions that break the underlying crystalline symmetry can form in interacting electronic systems. We examine the quantum Hall states that arise in high magnetic fields from anisotropic hole pockets on the Bi(111) surface. Spectroscopy performed with a scanning tunneling microscope shows that a combination of local strain and many-body Coulomb interactions lift th… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1610.07613v1-abstract-full').style.display = 'inline'; document.getElementById('1610.07613v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1610.07613v1-abstract-full" style="display: none;"> Nematic quantum fluids with wavefunctions that break the underlying crystalline symmetry can form in interacting electronic systems. We examine the quantum Hall states that arise in high magnetic fields from anisotropic hole pockets on the Bi(111) surface. Spectroscopy performed with a scanning tunneling microscope shows that a combination of local strain and many-body Coulomb interactions lift the six-fold Landau level (LL) degeneracy to form three valley-polarized quantum Hall states. We image the resulting anisotropic LL wavefunctions and show that they have a different orientation for each broken-symmetry state. The wavefunctions correspond precisely to those expected from pairs of hole valleys and provide a direct spatial signature of a nematic electronic phase. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1610.07613v1-abstract-full').style.display = 'none'; document.getElementById('1610.07613v1-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 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">Journal ref:</span> Science, 354, 316-321 (2016) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1610.07197">arXiv:1610.07197</a> <span> [<a href="https://arxiv.org/pdf/1610.07197">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/10.1088/1367-2630/18/10/105003">10.1088/1367-2630/18/10/105003 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Imaging electronic states on topological semimetals using scanning tunneling microscopy </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Gyenis%2C+A">Andras Gyenis</a>, <a href="/search/cond-mat?searchtype=author&query=Inoue%2C+H">Hiroyuki Inoue</a>, <a href="/search/cond-mat?searchtype=author&query=Jeon%2C+S">Sangjun Jeon</a>, <a href="/search/cond-mat?searchtype=author&query=Zhou%2C+B+B">Brian B. Zhou</a>, <a href="/search/cond-mat?searchtype=author&query=Feldman%2C+B+E">Benjamin E. Feldman</a>, <a href="/search/cond-mat?searchtype=author&query=Wang%2C+Z">Zhijun Wang</a>, <a href="/search/cond-mat?searchtype=author&query=Li%2C+J">Jian Li</a>, <a href="/search/cond-mat?searchtype=author&query=Jiang%2C+S">Shan Jiang</a>, <a href="/search/cond-mat?searchtype=author&query=Gibson%2C+Q+D">Quinn D. Gibson</a>, <a href="/search/cond-mat?searchtype=author&query=Kushwaha%2C+S+K">Satya K. Kushwaha</a>, <a href="/search/cond-mat?searchtype=author&query=Krizan%2C+J+W">Jason W. Krizan</a>, <a href="/search/cond-mat?searchtype=author&query=Ni%2C+N">Ni Ni</a>, <a href="/search/cond-mat?searchtype=author&query=Cava%2C+R+J">Robert J. Cava</a>, <a href="/search/cond-mat?searchtype=author&query=Bernevig%2C+B+A">B. Andrei Bernevig</a>, <a href="/search/cond-mat?searchtype=author&query=Yazdani%2C+A">Ali Yazdani</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="1610.07197v2-abstract-short" style="display: inline;"> Following the intense studies on topological insulators, significant efforts have recently been devoted to the search for gapless topological systems. These materials not only broaden the topological classification of matter but also provide a condensed matter realization of various relativistic particles and phenomena previously discussed mainly in high energy physics. Weyl semimetals host massle… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1610.07197v2-abstract-full').style.display = 'inline'; document.getElementById('1610.07197v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1610.07197v2-abstract-full" style="display: none;"> Following the intense studies on topological insulators, significant efforts have recently been devoted to the search for gapless topological systems. These materials not only broaden the topological classification of matter but also provide a condensed matter realization of various relativistic particles and phenomena previously discussed mainly in high energy physics. Weyl semimetals host massless, chiral, low-energy excitations in the bulk electronic band structure, whereas a symmetry protected pair of Weyl fermions gives rise to massless Dirac fermions. We employed scanning tunneling microscopy/spectroscopy to explore the behavior of electronic states both on the surface and in the bulk of topological semimetal phases. By mapping the quasiparticle interference and emerging Landau levels at high magnetic field in Dirac semimetals Cd$_3$As$_2$ and Na$_3$Bi, we observed extended Dirac-like bulk electronic bands. Quasiparticle interference imaged on Weyl semimetal TaAs demonstrated the predicted momentum dependent delocalization of Fermi arc surface states in the vicinity of the surface-projected Weyl nodes. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1610.07197v2-abstract-full').style.display = 'none'; document.getElementById('1610.07197v2-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 October, 2016; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 23 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">Journal ref:</span> New J. Phys. 18, 105003 (2016) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1603.04370">arXiv:1603.04370</a> <span> [<a href="https://arxiv.org/pdf/1603.04370">pdf</a>, <a href="https://arxiv.org/format/1603.04370">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Superconductivity">cond-mat.supr-con</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/10.1103/PhysRevB.93.161115">10.1103/PhysRevB.93.161115 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Scanning Josephson spectroscopy on the atomic scale </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Randeria%2C+M+T">Mallika T. Randeria</a>, <a href="/search/cond-mat?searchtype=author&query=Feldman%2C+B+E">Benjamin E. Feldman</a>, <a href="/search/cond-mat?searchtype=author&query=Drozdov%2C+I+K">Ilya K. Drozdov</a>, <a href="/search/cond-mat?searchtype=author&query=Yazdani%2C+A">Ali Yazdani</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="1603.04370v1-abstract-short" style="display: inline;"> The Josephson effect provides a direct method to probe the strength of the pairing interaction in superconductors. By measuring the phase fluctuating Josephson current between a superconducting tip of a scanning tunneling microscope (STM) and a BCS superconductor with isolated magnetic adatoms on its surface, we demonstrate that the spatial variation of the pairing order parameter can be character… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1603.04370v1-abstract-full').style.display = 'inline'; document.getElementById('1603.04370v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1603.04370v1-abstract-full" style="display: none;"> The Josephson effect provides a direct method to probe the strength of the pairing interaction in superconductors. By measuring the phase fluctuating Josephson current between a superconducting tip of a scanning tunneling microscope (STM) and a BCS superconductor with isolated magnetic adatoms on its surface, we demonstrate that the spatial variation of the pairing order parameter can be characterized on the atomic scale. This system provides an example where the local pairing potential suppression is not directly reflected in the spectra measured via quasipartcile tunneling. Spectroscopy with such superconducting tips also show signatures of previously unexplored Andreev processes through individual impurity-bound Shiba states. The atomic resolution achieved here establishes scanning Josephson spectroscopy as a promising technique for the study of novel superconducting phases. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1603.04370v1-abstract-full').style.display = 'none'; document.getElementById('1603.04370v1-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 March, 2016; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2016. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1502.03547">arXiv:1502.03547</a> <span> [<a href="https://arxiv.org/pdf/1502.03547">pdf</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/10.1063/1.4908158">10.1063/1.4908158 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Bulk crystal growth and electronic characterization of the 3D Dirac Semimetal Na3Bi </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Kushwaha%2C+S+K">Satya K. Kushwaha</a>, <a href="/search/cond-mat?searchtype=author&query=Krizan%2C+J+W">Jason W. Krizan</a>, <a href="/search/cond-mat?searchtype=author&query=Feldman%2C+B+E">Benjamin E. Feldman</a>, <a href="/search/cond-mat?searchtype=author&query=Gyenis%2C+A">Andras Gyenis</a>, <a href="/search/cond-mat?searchtype=author&query=Randeria%2C+M+T">Mallika T. Randeria</a>, <a href="/search/cond-mat?searchtype=author&query=Xiong%2C+J">Jun Xiong</a>, <a href="/search/cond-mat?searchtype=author&query=Xu%2C+S">Su-Yang Xu</a>, <a href="/search/cond-mat?searchtype=author&query=Alidoust%2C+N">Nasser Alidoust</a>, <a href="/search/cond-mat?searchtype=author&query=Belopolski%2C+I">Ilya Belopolski</a>, <a href="/search/cond-mat?searchtype=author&query=Liang%2C+T">Tian Liang</a>, <a href="/search/cond-mat?searchtype=author&query=Hasan%2C+M+Z">M. Zahid Hasan</a>, <a href="/search/cond-mat?searchtype=author&query=Ong%2C+N+P">N. P. Ong</a>, <a href="/search/cond-mat?searchtype=author&query=Yazdani%2C+A">A. Yazdani</a>, <a href="/search/cond-mat?searchtype=author&query=Cava%2C+R+J">R. J. Cava</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="1502.03547v1-abstract-short" style="display: inline;"> High quality hexagon plate-like Na3Bi crystals with large (001) plane surfaces were grown from a molten Na flux. The freshly cleaved crystals were analyzed by low temperature scanning tunneling microscopy (STM) and angle-resolved photoemission spectroscopy (ARPES), allowing for the characterization of the three-dimensional (3D) Dirac semimetal (TDS) behavior and the observation of the topological… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1502.03547v1-abstract-full').style.display = 'inline'; document.getElementById('1502.03547v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1502.03547v1-abstract-full" style="display: none;"> High quality hexagon plate-like Na3Bi crystals with large (001) plane surfaces were grown from a molten Na flux. The freshly cleaved crystals were analyzed by low temperature scanning tunneling microscopy (STM) and angle-resolved photoemission spectroscopy (ARPES), allowing for the characterization of the three-dimensional (3D) Dirac semimetal (TDS) behavior and the observation of the topological surface states. Landau levels (LL) were observed, and the energy-momentum relations exhibited a linear dispersion relationship, characteristic of the 3D TDS nature of Na3Bi. In transport measurements on Na3Bi crystals the linear magnetoresistance and Shubnikov-de Haas (SdH) quantum oscillations are observed for the first time. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1502.03547v1-abstract-full').style.display = 'none'; document.getElementById('1502.03547v1-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 February, 2015; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 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">To be published in a special issue of APL Materials</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> APL Mater. 3, 041504 (2015) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1403.3446">arXiv:1403.3446</a> <span> [<a href="https://arxiv.org/pdf/1403.3446">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> <span class="tag is-small is-grey 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="Strongly Correlated Electrons">cond-mat.str-el</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/nmat4023">10.1038/nmat4023 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Landau Quantization and Quasiparticle Interference in the Three-Dimensional Dirac Semimetal Cd3As2 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Jeon%2C+S">Sangjun Jeon</a>, <a href="/search/cond-mat?searchtype=author&query=Zhou%2C+B+B">Brian B. Zhou</a>, <a href="/search/cond-mat?searchtype=author&query=Gyenis%2C+A">Andras Gyenis</a>, <a href="/search/cond-mat?searchtype=author&query=Feldman%2C+B+E">Benjamin E. Feldman</a>, <a href="/search/cond-mat?searchtype=author&query=Kimchi%2C+I">Itamar Kimchi</a>, <a href="/search/cond-mat?searchtype=author&query=Potter%2C+A+C">Andrew C. Potter</a>, <a href="/search/cond-mat?searchtype=author&query=Gibson%2C+Q+D">Quinn D. Gibson</a>, <a href="/search/cond-mat?searchtype=author&query=Cava%2C+R+J">Robert J. Cava</a>, <a href="/search/cond-mat?searchtype=author&query=Vishwanath%2C+A">Ashvin Vishwanath</a>, <a href="/search/cond-mat?searchtype=author&query=Yazdani%2C+A">Ali Yazdani</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="1403.3446v2-abstract-short" style="display: inline;"> Condensed matter systems provide a rich setting to realize Dirac and Majorana fermionic excitations and the possibility to manipulate them in materials for potential applications. Recently, it has been proposed that Weyl fermions, which are chiral, massless particles, can emerge in certain bulk materials or in topological insulator multilayers and can produce unusual transport properties, such as… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1403.3446v2-abstract-full').style.display = 'inline'; document.getElementById('1403.3446v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1403.3446v2-abstract-full" style="display: none;"> Condensed matter systems provide a rich setting to realize Dirac and Majorana fermionic excitations and the possibility to manipulate them in materials for potential applications. Recently, it has been proposed that Weyl fermions, which are chiral, massless particles, can emerge in certain bulk materials or in topological insulator multilayers and can produce unusual transport properties, such as charge pumping driven by a chiral anomaly. A pair of Weyl fermions protected by crystalline symmetry, effectively forming a massless Dirac fermion, has been predicted to appear as low energy excitations in a number of candidate materials termed three-dimensional (3D) Dirac semimetals. Here we report scanning tunneling microscopy (STM) measurements at sub-Kelvin temperatures and high magnetic fields on one promising host material, the II-V semiconductor Cd3As2. Our study provides the first atomic scale probe of Cd3As2, showing that defects mostly influence the valence band, consistent with the observation of ultra-high mobility carriers in the conduction band. By combining Landau level spectroscopy and quasiparticle interference (QPI), we distinguish a large spin-splitting of the conduction band in a magnetic field and its extended Dirac-like dispersion above the expected regime. A model band structure consistent with our experimental findings suggests that for a specific orientation of the applied magnetic field, Weyl fermions are the low-energy excitations in Cd3As2. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1403.3446v2-abstract-full').style.display = 'none'; document.getElementById('1403.3446v2-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 June, 2014; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 13 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">Main Text: 17 pages, 4 figures. Supplementary Materials: 12 pages, 7 figures, Nature Materials (2014)</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1312.7033">arXiv:1312.7033</a> <span> [<a href="https://arxiv.org/pdf/1312.7033">pdf</a>, <a href="https://arxiv.org/format/1312.7033">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> </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.1250270">10.1126/science.1250270 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Electron-Hole Asymmetric Integer and Fractional Quantum Hall Effect in Bilayer Graphene </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Kou%2C+A">Angela Kou</a>, <a href="/search/cond-mat?searchtype=author&query=Feldman%2C+B+E">Benjamin E. Feldman</a>, <a href="/search/cond-mat?searchtype=author&query=Levin%2C+A+J">Andrei J. Levin</a>, <a href="/search/cond-mat?searchtype=author&query=Halperin%2C+B+I">Bertrand I. Halperin</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=Yacoby%2C+A">Amir Yacoby</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="1312.7033v1-abstract-short" style="display: inline;"> The nature of fractional quantum Hall (FQH) states is determined by the interplay between the Coulomb interaction and the symmetries of the system. The unique combination of spin, valley, and orbital degeneracies in bilayer graphene is predicted to produce novel and tunable FQH ground states. Here we present local electronic compressibility measurements of the FQH effect in the lowest Landau level… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1312.7033v1-abstract-full').style.display = 'inline'; document.getElementById('1312.7033v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1312.7033v1-abstract-full" style="display: none;"> The nature of fractional quantum Hall (FQH) states is determined by the interplay between the Coulomb interaction and the symmetries of the system. The unique combination of spin, valley, and orbital degeneracies in bilayer graphene is predicted to produce novel and tunable FQH ground states. Here we present local electronic compressibility measurements of the FQH effect in the lowest Landau level of bilayer graphene. We observe incompressible FQH states at filling factors v = 2p + 2/3 with hints of additional states appearing at v = 2p + 3/5, where p = -2,-1, 0, and 1. This sequence of states breaks particle-hole symmetry and instead obeys a v --> v + 2 symmetry, which highlights the importance of the orbital degeneracy for many-body states in bilayer graphene. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1312.7033v1-abstract-full').style.display = 'none'; document.getElementById('1312.7033v1-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 December, 2013; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 2013. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Science 345, 6192 (2014) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1303.5372">arXiv:1303.5372</a> <span> [<a href="https://arxiv.org/pdf/1303.5372">pdf</a>, <a href="https://arxiv.org/format/1303.5372">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> </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.88.115407">10.1103/PhysRevB.88.115407 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Fractional and integer quantum Hall effects in the zeroth Landau level in graphene </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Abanin%2C+D+A">Dmitry A. Abanin</a>, <a href="/search/cond-mat?searchtype=author&query=Feldman%2C+B+E">Benjamin E. Feldman</a>, <a href="/search/cond-mat?searchtype=author&query=Yacoby%2C+A">Amir Yacoby</a>, <a href="/search/cond-mat?searchtype=author&query=Halperin%2C+B+I">Bertrand I. Halperin</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="1303.5372v1-abstract-short" style="display: inline;"> Experiments on the fractional quantized Hall effect in the zeroth Landau level of graphene have revealed some striking differences between filling factors in the ranges 0<|谓|<1 and 1<|谓|<2. We argue that these differences can be largely understood as a consequence of the effects of terms in the Hamiltonian which break SU(2) valley symmetry, which we find to be important for |谓|<1 but negligible fo… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1303.5372v1-abstract-full').style.display = 'inline'; document.getElementById('1303.5372v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1303.5372v1-abstract-full" style="display: none;"> Experiments on the fractional quantized Hall effect in the zeroth Landau level of graphene have revealed some striking differences between filling factors in the ranges 0<|谓|<1 and 1<|谓|<2. We argue that these differences can be largely understood as a consequence of the effects of terms in the Hamiltonian which break SU(2) valley symmetry, which we find to be important for |谓|<1 but negligible for |谓| >1. The effective absence of valley anisotropy for |谓|>1 means that states with odd numerator, e.g. |谓|=5/3 or 7/5 can accommodate charged excitations in the form of large valley skyrmions, which have a low energy cost, and may be easily induced by coupling to impurities. The absence of observed quantum Hall states at these fractions is likely due to the effects of valley skyrmions. For |谓|<1, the anisotropy terms favor phases in which electrons occupy states with opposite spins, similar to the antiferromagnetic state previously hypothesized to be the ground state at 谓=0. The anisotropy and Zeeman energies suppress large-area skyrmions, so that quantized Hall states can be observable at a set of fractions similar to those in GaAs two-dimensional electron systems. In a perpendicular magnetic field B, the competition between the Coulomb energy, which varies as B^{1/2}, and the Zeeman energy, which varies as B, can explain the observation of apparent phase transitions as a function of B for fixed 谓, as transitions between states with different degrees of spin polarization. In addition to an analysis of various fractional states, and an examination of the effects of disorder on valley skyrmions, we present new experimental data for the energy gaps at integer fillings 谓=0 and 谓= -1, as a function of magnetic field, and we examine the possibility that valley-skyrmions may account for the smaller energy gaps observed at 谓= -1. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1303.5372v1-abstract-full').style.display = 'none'; document.getElementById('1303.5372v1-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 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">Comments:</span> <span class="has-text-grey-dark mathjax">19 pages, 1 figure</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. B 88, 115407 (2013) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1303.0838">arXiv:1303.0838</a> <span> [<a href="https://arxiv.org/pdf/1303.0838">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/10.1103/PhysRevLett.111.076802">10.1103/PhysRevLett.111.076802 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Fractional Quantum Hall Phase Transitions and Four-flux Composite Fermions in Graphene </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Feldman%2C+B+E">Benjamin E. Feldman</a>, <a href="/search/cond-mat?searchtype=author&query=Levin%2C+A+J">Andrei J. Levin</a>, <a href="/search/cond-mat?searchtype=author&query=Krauss%2C+B">Benjamin Krauss</a>, <a href="/search/cond-mat?searchtype=author&query=Abanin%2C+D">Dmitry Abanin</a>, <a href="/search/cond-mat?searchtype=author&query=Halperin%2C+B+I">Bertrand. I. Halperin</a>, <a href="/search/cond-mat?searchtype=author&query=Smet%2C+J+H">Jurgen H. Smet</a>, <a href="/search/cond-mat?searchtype=author&query=Yacoby%2C+A">Amir Yacoby</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="1303.0838v1-abstract-short" style="display: inline;"> Graphene and its multilayers have attracted considerable interest owing to the fourfold spin and valley degeneracy of their charge carriers, which enables the formation of a rich variety of broken-symmetry states and raises the prospect of controlled phase transitions among them. In especially clean samples, electron-electron interactions were recently shown to produce surprising patterns of symme… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1303.0838v1-abstract-full').style.display = 'inline'; document.getElementById('1303.0838v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1303.0838v1-abstract-full" style="display: none;"> Graphene and its multilayers have attracted considerable interest owing to the fourfold spin and valley degeneracy of their charge carriers, which enables the formation of a rich variety of broken-symmetry states and raises the prospect of controlled phase transitions among them. In especially clean samples, electron-electron interactions were recently shown to produce surprising patterns of symmetry breaking and phase transitions in the integer quantum Hall regime. Although a series of robust fractional quantum Hall states was also recently observed in graphene, their rich phase diagram and tunability have yet to be fully explored. Here we report local electronic compressibility measurements of ultraclean suspended graphene that reveal a multitude of fractional quantum Hall states surrounding filling factors v = -1/2 and -1/4. In several of these states, we observe phase transitions that indicate abrupt changes in the underlying order and are marked by a narrow region of negative compressibility that cuts across the incompressible peak. Remarkably, as filling factor approaches v = -1/2, we observe additional oscillations in compressibility that appear to be related to the phase transitions and persist to within 2.5% of v = -1/2. We use a simple model based on crossing Landau levels of composite particles with different internal degrees of freedom to explain many qualitative features of the experimental data. Our results add to the diverse array of correlated states observed in graphene and demonstrate substantial control over their order parameters, showing that graphene serves as an excellent platform to study correlated electron phases of matter. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1303.0838v1-abstract-full').style.display = 'none'; document.getElementById('1303.0838v1-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 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> Phys. Rev. Lett. 111, 076802 (2013) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1201.5128">arXiv:1201.5128</a> <span> [<a href="https://arxiv.org/pdf/1201.5128">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/10.1126/science.1224784">10.1126/science.1224784 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Unconventional Sequence of Fractional Quantum Hall States in Suspended Graphene </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Feldman%2C+B+E">Benjamin E. Feldman</a>, <a href="/search/cond-mat?searchtype=author&query=Krauss%2C+B">Benjamin Krauss</a>, <a href="/search/cond-mat?searchtype=author&query=Smet%2C+J+H">Jurgen H. Smet</a>, <a href="/search/cond-mat?searchtype=author&query=Yacoby%2C+A">Amir Yacoby</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="1201.5128v1-abstract-short" style="display: inline;"> Interactions among electrons can give rise to striking collective phenomena when the kinetic energy of charge carriers is suppressed. One example is the fractional quantum Hall effect, in which correlations between electrons moving in two dimensions under the influence of a strong magnetic field generate excitations with fractional charge. Graphene provides a platform to study unique many-body eff… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1201.5128v1-abstract-full').style.display = 'inline'; document.getElementById('1201.5128v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1201.5128v1-abstract-full" style="display: none;"> Interactions among electrons can give rise to striking collective phenomena when the kinetic energy of charge carriers is suppressed. One example is the fractional quantum Hall effect, in which correlations between electrons moving in two dimensions under the influence of a strong magnetic field generate excitations with fractional charge. Graphene provides a platform to study unique many-body effects due to its massless chiral charge carriers and the fourfold degeneracy that arises from their spin and valley degrees of freedom. Here we report local electronic compressibility measurements of a suspended graphene flake performed using a scanning single-electron transistor. Between Landau level filling v = 0 and 1, we observe incompressible fractional quantum Hall states that follow the standard composite fermion sequence v = p/(2p \pm 1) for all integer p \leq 4. In contrast, incompressible behavior occurs only at v = 4/3, 8/5, 10/7 and 14/9 between v = 1 and 2. These fractions correspond to a subset of the standard composite fermion sequence involving only even numerators, suggesting a robust underlying symmetry. We extract the energy gaps associated with each fractional quantum Hall state as a function of magnetic field. The states at v = 1/3, 2/3, 4/3 and 8/5 are the strongest at low field, and persist below 1.5 T. The unusual sequence of incompressible states provides insight into the interplay between electronic correlations and SU(4) symmetry in graphene. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1201.5128v1-abstract-full').style.display = 'none'; document.getElementById('1201.5128v1-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 January, 2012; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2012. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Science 337, 1196-1199 (2012) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1010.0989">arXiv:1010.0989</a> <span> [<a href="https://arxiv.org/pdf/1010.0989">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/10.1126/science.1194988">10.1126/science.1194988 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Coulomb-driven broken-symmetry states in doubly gated suspended bilayer graphene </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Weitz%2C+R+T">R. Thomas Weitz</a>, <a href="/search/cond-mat?searchtype=author&query=Allen%2C+M+T">Monica T. Allen</a>, <a href="/search/cond-mat?searchtype=author&query=Feldman%2C+B+E">Benjamin E. Feldman</a>, <a href="/search/cond-mat?searchtype=author&query=Martin%2C+J">Jens Martin</a>, <a href="/search/cond-mat?searchtype=author&query=Yacoby%2C+A">Amir Yacoby</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="1010.0989v1-abstract-short" style="display: inline;"> The non-interacting energy spectrum of graphene and its bilayer counterpart consists of multiple degeneracies owing to the inherent spin, valley and layer symmetries. Interactions among charge carriers are expected to spontaneously break these symmetries, leading to gapped ordered states. In the quantum Hall regime these states are predicted to be ferromagnetic in nature whereby the system becomes… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1010.0989v1-abstract-full').style.display = 'inline'; document.getElementById('1010.0989v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1010.0989v1-abstract-full" style="display: none;"> The non-interacting energy spectrum of graphene and its bilayer counterpart consists of multiple degeneracies owing to the inherent spin, valley and layer symmetries. Interactions among charge carriers are expected to spontaneously break these symmetries, leading to gapped ordered states. In the quantum Hall regime these states are predicted to be ferromagnetic in nature whereby the system becomes spin polarized, layer polarized or both. In bilayer graphene, due to its parabolic dispersion, interaction-induced symmetry breaking is already expected at zero magnetic field. In this work, the underlying order of the various broken-symmetry states is investigated in bilayer graphene that is suspended between top and bottom gate electrodes. By controllably breaking the spin and sublattice symmetries we are able to deduce the order parameter of the various quantum Hall ferromagnetic states. At small carrier densities, we identify for the first time three distinct broken symmetry states, one of which is consistent with either spontaneously broken time-reversal symmetry or spontaneously broken rotational symmetry. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1010.0989v1-abstract-full').style.display = 'none'; document.getElementById('1010.0989v1-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> 5 October, 2010; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2010. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1009.2069">arXiv:1009.2069</a> <span> [<a href="https://arxiv.org/pdf/1009.2069">pdf</a>, <a href="https://arxiv.org/format/1009.2069">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/PhysRevLett.105.256806">10.1103/PhysRevLett.105.256806 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Local Compressibility Measurements of Correlated States in Suspended Bilayer Graphene </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Martin%2C+J">Jens Martin</a>, <a href="/search/cond-mat?searchtype=author&query=Feldman%2C+B+E">Benjamin E. Feldman</a>, <a href="/search/cond-mat?searchtype=author&query=Weitz%2C+R+T">R. Thomas Weitz</a>, <a href="/search/cond-mat?searchtype=author&query=Allen%2C+M+T">Monica T. Allen</a>, <a href="/search/cond-mat?searchtype=author&query=Yacoby%2C+A">Amir Yacoby</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="1009.2069v1-abstract-short" style="display: inline;"> Bilayer graphene has attracted considerable interest due to the important role played by many-body effects, particularly at low energies. Here we report local compressibility measurements of a suspended graphene bilayer. We find that the energy gaps at filling factors v = 4 do not vanish at low fields, but instead merge into an incompressible region near the charge neutrality point at zero electri… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1009.2069v1-abstract-full').style.display = 'inline'; document.getElementById('1009.2069v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1009.2069v1-abstract-full" style="display: none;"> Bilayer graphene has attracted considerable interest due to the important role played by many-body effects, particularly at low energies. Here we report local compressibility measurements of a suspended graphene bilayer. We find that the energy gaps at filling factors v = 4 do not vanish at low fields, but instead merge into an incompressible region near the charge neutrality point at zero electric and magnetic field. These results indicate the existence of a zero-field ordered state and are consistent with the formation of either an anomalous quantum Hall state or a nematic phase with broken rotational symmetry. At higher fields, we measure the intrinsic energy gaps of broken-symmetry states at v = 0, 1 and 2, and find that they scale linearly with magnetic field, yet another manifestation of the strong Coulomb interactions in bilayer graphene. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1009.2069v1-abstract-full').style.display = 'none'; document.getElementById('1009.2069v1-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> 10 September, 2010; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2010. </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">9 pages, including 4 figures and supplementary materials</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Phys. Rev. Lett. 105, 256806 (2010) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/0909.2883">arXiv:0909.2883</a> <span> [<a href="https://arxiv.org/pdf/0909.2883">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/nphys1406">10.1038/nphys1406 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Broken symmetry states and divergent resistance in suspended bilayer graphene </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/cond-mat?searchtype=author&query=Feldman%2C+B+E">Benjamin E. Feldman</a>, <a href="/search/cond-mat?searchtype=author&query=Martin%2C+J">Jens Martin</a>, <a href="/search/cond-mat?searchtype=author&query=Yacoby%2C+A">Amir Yacoby</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="0909.2883v1-abstract-short" style="display: inline;"> Graphene [1] and its bilayer have generated tremendous excitement in the physics community due to their unique electronic properties [2]. The intrinsic physics of these materials, however, is partially masked by disorder, which can arise from various sources such as ripples [3] or charged impurities [4]. Recent improvements in quality have been achieved by suspending graphene flakes [5,6], yield… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0909.2883v1-abstract-full').style.display = 'inline'; document.getElementById('0909.2883v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="0909.2883v1-abstract-full" style="display: none;"> Graphene [1] and its bilayer have generated tremendous excitement in the physics community due to their unique electronic properties [2]. The intrinsic physics of these materials, however, is partially masked by disorder, which can arise from various sources such as ripples [3] or charged impurities [4]. Recent improvements in quality have been achieved by suspending graphene flakes [5,6], yielding samples with very high mobilities and little charge inhomogeneity. Here we report the fabrication of suspended bilayer graphene devices with very little disorder. We observe fully developed quantized Hall states at magnetic fields of 0.2 T, as well as broken symmetry states at intermediate filling factors $谓= 0$, $\pm 1$, $\pm 2$ and $\pm 3$. The devices exhibit extremely high resistance in the $谓= 0$ state that grows with magnetic field and scales as magnetic field divided by temperature. This resistance is predominantly affected by the perpendicular component of the applied field, indicating that the broken symmetry states arise from many-body interactions. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0909.2883v1-abstract-full').style.display = 'none'; document.getElementById('0909.2883v1-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> 15 September, 2009; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2009. </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">23 pages, including 4 figures and supplementary information; accepted to Nature Physics</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Nature Physics 5, 889 - 893 (2009) </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 22.4 17.4 52.1 39.5 154.1 113.6 21.1 15.4 56.7 47.8 92.2 47.6 35.7.3 72-32.8 92.3-47.6 102-74.1 131.6-96.3 154-113.7zM256 320c23.2.4 56.6-29.2 73.4-41.4 132.7-96.3 142.8-104.7 173.4-128.7 5.8-4.5 9.2-11.5 9.2-18.9v-19c0-26.5-21.5-48-48-48H48C21.5 64 0 85.5 0 112v19c0 7.4 3.4 14.3 9.2 18.9 30.6 23.9 40.7 32.4 173.4 128.7 16.8 12.2 50.2 41.8 73.4 41.4z"/></svg> <a href="https://info.arxiv.org/help/contact.html"> Contact</a> </li> <li> <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 512 512" class="icon filter-black" role="presentation"><title>subscribe to arXiv mailings</title><desc>Click here to subscribe</desc><path d="M476 3.2L12.5 270.6c-18.1 10.4-15.8 35.6 2.2 43.2L121 358.4l287.3-253.2c5.5-4.9 13.3 2.6 8.6 8.3L176 407v80.5c0 23.6 28.5 32.9 42.5 15.8L282 426l124.6 52.2c14.2 6 30.4-2.9 33-18.2l72-432C515 7.8 493.3-6.8 476 3.2z"/></svg> <a href="https://info.arxiv.org/help/subscribe"> Subscribe</a> </li> </ul> </div> </div> </div>   <div class="column"> <div class="columns"> <div class="column"> <ul class="nav-spaced"> <li><a href="https://info.arxiv.org/help/license/index.html">Copyright</a></li> <li><a href="https://info.arxiv.org/help/policies/privacy_policy.html">Privacy Policy</a></li> </ul> </div> <div class="column sorry-app-links"> <ul class="nav-spaced"> <li><a href="https://info.arxiv.org/help/web_accessibility.html">Web Accessibility Assistance</a></li> <li> <p class="help"> <a class="a11y-main-link" href="https://status.arxiv.org" target="_blank">arXiv Operational Status <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 256 512" class="icon filter-dark_grey" role="presentation"><path d="M224.3 273l-136 136c-9.4 9.4-24.6 9.4-33.9 0l-22.6-22.6c-9.4-9.4-9.4-24.6 0-33.9l96.4-96.4-96.4-96.4c-9.4-9.4-9.4-24.6 0-33.9L54.3 103c9.4-9.4 24.6-9.4 33.9 0l136 136c9.5 9.4 9.5 24.6.1 34z"/></svg></a><br> Get status notifications via <a class="is-link" href="https://subscribe.sorryapp.com/24846f03/email/new" target="_blank"><svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 512 512" class="icon filter-black" role="presentation"><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 22.4 17.4 52.1 39.5 154.1 113.6 21.1 15.4 56.7 47.8 92.2 47.6 35.7.3 72-32.8 92.3-47.6 102-74.1 131.6-96.3 154-113.7zM256 320c23.2.4 56.6-29.2 73.4-41.4 132.7-96.3 142.8-104.7 173.4-128.7 5.8-4.5 9.2-11.5 9.2-18.9v-19c0-26.5-21.5-48-48-48H48C21.5 64 0 85.5 0 112v19c0 7.4 3.4 14.3 9.2 18.9 30.6 23.9 40.7 32.4 173.4 128.7 16.8 12.2 50.2 41.8 73.4 41.4z"/></svg>email</a> or <a class="is-link" href="https://subscribe.sorryapp.com/24846f03/slack/new" target="_blank"><svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 448 512" class="icon filter-black" role="presentation"><path d="M94.12 315.1c0 25.9-21.16 47.06-47.06 47.06S0 341 0 315.1c0-25.9 21.16-47.06 47.06-47.06h47.06v47.06zm23.72 0c0-25.9 21.16-47.06 47.06-47.06s47.06 21.16 47.06 47.06v117.84c0 25.9-21.16 47.06-47.06 47.06s-47.06-21.16-47.06-47.06V315.1zm47.06-188.98c-25.9 0-47.06-21.16-47.06-47.06S139 32 164.9 32s47.06 21.16 47.06 47.06v47.06H164.9zm0 23.72c25.9 0 47.06 21.16 47.06 47.06s-21.16 47.06-47.06 47.06H47.06C21.16 243.96 0 222.8 0 196.9s21.16-47.06 47.06-47.06H164.9zm188.98 47.06c0-25.9 21.16-47.06 47.06-47.06 25.9 0 47.06 21.16 47.06 47.06s-21.16 47.06-47.06 47.06h-47.06V196.9zm-23.72 0c0 25.9-21.16 47.06-47.06 47.06-25.9 0-47.06-21.16-47.06-47.06V79.06c0-25.9 21.16-47.06 47.06-47.06 25.9 0 47.06 21.16 47.06 47.06V196.9zM283.1 385.88c25.9 0 47.06 21.16 47.06 47.06 0 25.9-21.16 47.06-47.06 47.06-25.9 0-47.06-21.16-47.06-47.06v-47.06h47.06zm0-23.72c-25.9 0-47.06-21.16-47.06-47.06 0-25.9 21.16-47.06 47.06-47.06h117.84c25.9 0 47.06 21.16 47.06 47.06 0 25.9-21.16 47.06-47.06 47.06H283.1z"/></svg>slack</a> </p> </li> </ul> </div> </div> </div>  </div> </footer> <script src="https://static.arxiv.org/static/base/1.0.0a5/js/member_acknowledgement.js"></script> </body> </html>

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