Helical Edge States and Quantum Phase Transitions in Tetralayer Graphene
Helical Edge States and Quantum Phase Transitions in Tetralayer Graphene
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DOI：
10.1103/physrevlett.125.036803
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发表时间：
2020-07-13
影响因子：
8.6
通讯作者：
Fertig, Herbert A.
中科院分区：
文献类型：
--
作者：
Che, Shi;Shi, Yanmeng;Fertig, Herbert A.
具有自旋-动量锁定的螺旋导体是一种很有前途的马约拉纳费米子平台。在这里，我们报道了在霍尔棒和科尔比诺几何结构中观察到两个不同的拓扑结构相，支持带电的螺旋边缘态，中性Bernal堆积的四层石墨烯。当磁场B垂直于面外位移场D变化时，我们观察到一个由绝缘相和两个金属相组成的相图，分别有0，1和2个螺旋边缘态。这些相被一个理论模型所解释，该模型将它们的电导与自旋极化平台联系起来。它们之间的跃迁源于层间跃迁、静电和交换相互作用能之间的竞争。我们的工作突出了几层石墨烯中复杂的竞争对称性和丰富的量子相。
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-perpendicular to 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 interlayer hopping, electrostatic and exchange interaction energies. Our work highlights the complex competing symmetries and the rich quantum phases in few-layer graphene.