Gong Ming, Liu Haiwen, Jiang Hua, Chen Chui-Zhen, Xie X-C
International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China.
Center for Advanced Quantum Studies, Department of Physics, Beijing Normal University, Beijing 100875, China.
Natl Sci Rev. 2023 Feb 6;10(9):nwad025. doi: 10.1093/nsr/nwad025. eCollection 2023 Sep.
Fractional quantization can emerge in noncorrelated systems due to the parity anomaly, while its condensed matter realization is a challenging problem. We propose that in axion insulators (AIs), parity anomaly manifests a unique fractional boundary excitation: the half-quantized helical hinge currents. These helical hinge currents microscopically originate from the lateral Goos-Hänchen (GH) shift of massless side-surface Dirac electrons that are totally reflected from the hinges. Meanwhile, due to the presence of the massive top and bottom surfaces of the AI, the helical current induced by the GH shift is half-quantized. The semiclassical wave packet analysis uncovers that the hinge current has a topological origin and its half quantization is robust to parameter variations. Lastly, we propose an experimentally feasible six-terminal device to identify the half-quantized hinge channels by measuring the nonreciprocal conductances. Our results advance the realization of the half-quantization and topological magnetoelectric responses in AIs.
由于宇称反常，分数阶量子化可出现在非相关系统中，而其在凝聚态物质中的实现是一个具有挑战性的问题。我们提出，在轴子绝缘体（AI）中，宇称反常表现为一种独特的分数边界激发：半量子化的螺旋铰链电流。这些螺旋铰链电流在微观上起源于从铰链全反射的无质量侧面狄拉克电子的横向古斯 - 汉欣（GH）位移。同时，由于AI存在有质量的顶面和底面，由GH位移诱导的螺旋电流是半量子化的。半经典波包分析揭示，铰链电流具有拓扑起源，并且其半量子化对参数变化具有鲁棒性。最后，我们提出一种实验上可行的六端器件，通过测量非互易电导来识别半量子化的铰链通道。我们的结果推动了AI中半量子化和拓扑磁电响应的实现。
