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arXiv · 2006.09351

Helical Edge States and Quantum Phase Transitions in Tetralayer Graphene

Shi Che·Yanmeng Shi·Jiawei Yang·Haidong Tian·Ruoyu Chen·Takashi Taniguchi·Kenji Watanabe·Dmitry Smirnov·Chun Ning Lau·Efrat Shimshoni·Ganpathy Murthy·Herbert A. Fertig
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Abstract

Helical conductors with spin-momentum locking are promising platforms for Majorana fermions. Here we report observation of two topologically distinct phases supporting helical edge states in charge neutral Bernal-stacked tetralayer graphene in Hall bar and Corbino geometries. As the magnetic field B and out-of-plane displacement field D are varied, we observe a phase diagram consisting of an insulating phase and two metallic phases, with 0, 1 and 2 helical edge states, respectively. These phases are accounted for by a theoretical model that relates their conductance to spin-polarization plateaus. Transitions between them arise from a competition among inter-layer hopping, electrostatic and exchange interaction energies. Our work highlights the complex competing symmetries and the rich quantum phases in few-layer graphene.

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Shi Che, Yanmeng Shi, Jiawei Yang, Haidong Tian, Ruoyu Chen, Takashi Taniguchi, Kenji Watanabe, Dmitry Smirnov, Chun Ning Lau, Efrat Shimshoni, Ganpathy Murthy, Herbert A. Fertig. 2020-06-16. Helical Edge States and Quantum Phase Transitions in Tetralayer Graphene. https://doi.org/10.1103/physrevlett.125.036803

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