碲烯中的本征线偏振光电流与光导效应的机制分离

Separation of Intrinsic Linear Photogalvanic Effect and Photoconductive Effect in Tellurene

摘要: 碲烯(Te)具有手性结构和D3点群对称性，其价带顶附近的Weyl锥为研究非线性光电流效应提供了理想平台。在低对称性材料中，光电流通常来源于本征线偏振光电流(LPGE)与光导效应的共存，但如何有效区分两者沿不同晶向的贡献仍是当前难点。本研究采用非对称电极设计，在碲烯器件中独立激发和测量沿a轴与c轴的线偏振光电流，通过系统考察零偏压与有偏压、低温与室温下的响应，建立了偏压依赖性、栅压响应特性和温度敏感性三个独立判据。实验发现：零偏压下LPGE在费米能级位于价带顶时最强；有偏压时纵向配置为LPGE与光导效应叠加，横向配置以光导效应为主，其栅压不对称性源于光吸收各向异性；温度对比进一步验证了光导效应的强温度敏感性。本研究为低对称性拓扑材料中光电流机制的解析提供了实验范式。

Abstract: Tellurene (Te) possesses a chiral structure with D3 point group symmetry, and its Weyl cones near the valence band maximum provide an ideal platform for investigating nonlinear photocurrent effects. In low-symmetry materials, photocurrents typically originate from the coexistence of intrinsic linear photogalvanic effect (LPGE) and photoconductive effects, yet effectively distinguishing their contributions along different crystal orientations remains a challenge. In this study, an asymmetric electrode design is employed to independently excite and measure linear photogalvanic currents along the a-axis and c-axis in tellurene devices. By systematically examining responses at zero bias and with applied bias, as well as at low temperature and room temperature, three independent criteria are established: bias dependence, gate voltage response characteristics, and temperature sensitivity. Experimental results show that under zero bias, LPGE is strongest when the Fermi level lies at the valence band maximum. With applied bias, the longitudinal configuration combines LPGE and photoconductive effects, while the transverse configuration is dominated by photoconductive effects, with its gate asymmetry originating from anisotropic light absorption. Temperature-dependent measurements further confirm the strong temperature sensitivity of photoconductive effects. This study provides an experimental paradigm for analyzing photocurrent mechanisms in low-symmetry topological materials.