Ji Zhurun, Liu Gerui, Addison Zachariah, Liu Wenjing, Yu Peng, Gao Heng, Liu Zheng, Rappe Andrew M, Kane Charles L, Mele Eugene J, Agarwal Ritesh
Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA, USA.
Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA, USA.
Nat Mater. 2019 Sep;18(9):955-962. doi: 10.1038/s41563-019-0421-5. Epub 2019 Jul 15.
Weyl semimetals (WSMs) are gapless topological states of matter with broken inversion and/or time reversal symmetry. WSMs can support a circulating photocurrent when illuminated by circularly polarized light at normal incidence. Here, we report a spatially dispersive circular photogalvanic effect (s-CPGE) in a WSM that occurs with a spatially varying beam profile. Our analysis shows that the s-CPGE is controlled by a symmetry selection rule combined with asymmetric carrier excitation and relaxation dynamics. By evaluating the s-CPGE for a minimal model of a WSM, a frequency-dependent scaling behaviour of the photocurrent is obtained. Wavelength-dependent measurements from the visible to mid-infrared range show evidence of Berry curvature singularities and band inversion in the s-CPGE response. We present the s-CPGE as a promising spectroscopic probe for topological band properties, with the potential for controlling photoresponse by patterning optical fields on topological materials to store, manipulate and transmit information.
外尔半金属（WSMs）是具有空间反演和/或时间反演对称性破缺的无带隙拓扑物态。当在垂直入射时被圆偏振光照射时，WSMs 能够支持一个循环光电流。在此，我们报道了在一种具有空间变化光束轮廓的 WSM 中发生的空间色散圆光电流效应（s-CPGE）。我们的分析表明，s-CPGE 由一个对称性选择规则与不对称的载流子激发和弛豫动力学共同控制。通过对一个 WSM 的最小模型评估 s-CPGE，获得了光电流的频率依赖标度行为。从可见光到中红外范围的波长依赖测量显示了 s-CPGE 响应中贝里曲率奇点和能带反转的证据。我们将 s-CPGE 展示为一种用于拓扑能带性质的有前景的光谱探测手段，具有通过在拓扑材料上对光场进行图案化来控制光响应以存储、操纵和传输信息的潜力。
