Shi Li-Kun, Zhang Dong, Chang Kai, Song Justin C W
Division of Physics and Applied Physics, Nanyang Technological University, Singapore 637371, Republic of Singapore.
Max Planck Institute for the Physics of Complex Systems, 01187 Dresden, Germany.
Phys Rev Lett. 2021 May 14;126(19):197402. doi: 10.1103/PhysRevLett.126.197402.
The nonlinear shift current, also known as the bulk photovoltaic current generated by linearly polarized light, has long been known to be absent in crystals with inversion symmetry. Here we argue that a nonzero shift current in centrosymmetric crystals can be activated by a photon-drag effect. Photon-drag shift current proceeds from a "shift current dipole" (a geometric quantity characterizing interband transitions) and manifests a purely transverse response in centrosymmetric crystals. This transverse nature proceeds directly from the shift-vector's pseudovector nature under mirror operation and underscores its intrinsic geometric origin. Photon-drag shift current can be greatly enhanced by coupling to polaritons and provides a new and sensitive tool to interrogate the subtle interband coherences of materials with inversion symmetry previously thought to be inaccessible via photocurrent probes.
非线性位移电流，也称为由线偏振光产生的体光伏电流，长期以来人们都知道在具有反演对称性的晶体中不存在这种电流。在此我们认为，中心对称晶体中的非零位移电流可以通过光子拖曳效应来激活。光子拖曳位移电流源自“位移电流偶极子”（一种表征带间跃迁的几何量），并且在中心对称晶体中表现出纯横向响应。这种横向特性直接源于位移矢量在镜面对称操作下的赝矢量性质，并突出了其内在的几何起源。通过与极化激元耦合，光子拖曳位移电流可以得到极大增强，并且提供了一种全新且灵敏的工具，用于探究具有反演对称性的材料中微妙的带间相干性，而此前人们认为通过光电流探针无法获取这些信息。
