Spontaneous and ferroelectric quantum Hall states in rhombohedral trilayer and bilayer graphene
ORAL · Invited
Abstract
The family of rhombohedral multilayer and bilayer graphenes has emerged as promising platform for investigation unconventional superconducting and correlated phases that have been observed as low-temperature ground states of spin-valley (isospin) polarized phases. Intriguingly, in these systems the ratio of Coulomb vs. kinetic energy of charge carriers can be controlled via dielectric engineering and displacement field.
In this talk, we discuss our recent findings of correlated states in ABC tri- and AB bilayer graphene. For example, when suspended in vacuum, they show a remarkable, electric field-controlled phase diagram of spontaneously broken-symmetry states near charge neutrality. In comparison, in conventional (h-BN encapsulated) samples due to the screened Coulomb interaction, no interacting phases are visible in ABC trilayer and AB bilayer [1] graphene. Because of their spontaneous orbital magnetizations, as revealed by the magnetic hysteresis behavior, the predicted quantum anomalous Hall and “ALL” competing ground states with Chern numbers ±3 in ABC [2]and ±2 in AB [3] and can be stabilized at vanishing but finite magnetic fields. At finite magnetic fields, the quantum Hall ferromagnets of the zeroth Landau level of ABC graphene are ferroelectrics with spontaneous layer polarizations, as evidenced by the electric hysteresis behavior [2]. We will finally also discuss results on encapsulated AB bilayer graphene in which at large displacement fields even at zero magnetic fields correlated states are visible that are consistent with anomalous Hall insulating (Wigner crystal) states [4][5].
[1] A. M. Seiler, N. Jacobsen, M. Statz, N. Fernandez, F. Falorsi, K. Watanabe, T. Taniguchi, Z. Dong, L. S. Levitov and R. T. Weitz, Nat. Commun. 15, 3133 (2024)
[2] F. Winterer, F. R. Geisenhof, N. Fernandez, A. M. Seiler, F. Zhang and R. T. Weitz, Nature Physics 20, 422–427 (2024)
[3] F. R. Geisenhof, F. Winterer, A. M. Seiler, J. Lenz, T. Xu, F. Zhang and R. T. Weitz, Nature 598, 53-58 (2021)
[4] A. M. Seiler, F. R. Geisenhof, F. Winterer, K. Watanabe, T. Taniguchi, T. Xu, F. Zhang and R. T. Weitz, Nature 608, 298–302 (2022)
[5] A. M. Seiler, M. Statz, C. Eckel, I. Weimer, J. F. Pöhls, K. Watanabe, T. Taniguchi, F. Zhang and R. T. Weitz, arXiv:2408.16628 (2024)
In this talk, we discuss our recent findings of correlated states in ABC tri- and AB bilayer graphene. For example, when suspended in vacuum, they show a remarkable, electric field-controlled phase diagram of spontaneously broken-symmetry states near charge neutrality. In comparison, in conventional (h-BN encapsulated) samples due to the screened Coulomb interaction, no interacting phases are visible in ABC trilayer and AB bilayer [1] graphene. Because of their spontaneous orbital magnetizations, as revealed by the magnetic hysteresis behavior, the predicted quantum anomalous Hall and “ALL” competing ground states with Chern numbers ±3 in ABC [2]and ±2 in AB [3] and can be stabilized at vanishing but finite magnetic fields. At finite magnetic fields, the quantum Hall ferromagnets of the zeroth Landau level of ABC graphene are ferroelectrics with spontaneous layer polarizations, as evidenced by the electric hysteresis behavior [2]. We will finally also discuss results on encapsulated AB bilayer graphene in which at large displacement fields even at zero magnetic fields correlated states are visible that are consistent with anomalous Hall insulating (Wigner crystal) states [4][5].
[1] A. M. Seiler, N. Jacobsen, M. Statz, N. Fernandez, F. Falorsi, K. Watanabe, T. Taniguchi, Z. Dong, L. S. Levitov and R. T. Weitz, Nat. Commun. 15, 3133 (2024)
[2] F. Winterer, F. R. Geisenhof, N. Fernandez, A. M. Seiler, F. Zhang and R. T. Weitz, Nature Physics 20, 422–427 (2024)
[3] F. R. Geisenhof, F. Winterer, A. M. Seiler, J. Lenz, T. Xu, F. Zhang and R. T. Weitz, Nature 598, 53-58 (2021)
[4] A. M. Seiler, F. R. Geisenhof, F. Winterer, K. Watanabe, T. Taniguchi, T. Xu, F. Zhang and R. T. Weitz, Nature 608, 298–302 (2022)
[5] A. M. Seiler, M. Statz, C. Eckel, I. Weimer, J. F. Pöhls, K. Watanabe, T. Taniguchi, F. Zhang and R. T. Weitz, arXiv:2408.16628 (2024)
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Presenters
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Thomas R Weitz
University of Göttingen, Georg-August University Göttingen
Authors
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Thomas R Weitz
University of Göttingen, Georg-August University Göttingen