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自旋电子学和谷电子学作为半导体物理的新方向, 旨在利用电子的自旋和谷自由度来实现新型的逻辑运算和信息处理. 是近年来研究自旋电子学和谷电子学的重要实验手段, 也是实现新型的自旋与谷存储器件的一个可能的方式, 为下一代的器件信息的处理方法提出了一种新的可能. 是一种二阶非线性光电响应, 是指材料在圆偏振光的激发下产生随偏振角度变化的光电流. 光电流的产生依赖于自旋、谷极化、对称性以及Berry曲率等诸多因素, 可以揭示出材料深层次的物理性质. 本篇综述主要讨论了在不同材料体系产生的主要机制, 包括在半导体异质结由对称性破缺导致的Rashba自旋轨道耦合引起的圆偏振光电流, 以及拓扑 Weyl半金属由Berry曲率以及泡利阻塞造成的电子动量选择, 以及二维层状过渡金属硫化物中圆偏振光产生的谷极化电流等. 在此基础上, 本文还简略介绍了一些新型二维材料中的的可能实现的方式, 以及一些潜在的应用.The spin and valley degree of freedom are a novel way to extend the functionalities of spintronic and valleytronic devices. A traditional, room-temperature way of examining the spin polarization generates the photocurrent whose magnitude and polarity depend on chirality of induced optical excitation. The circularly polarized photovoltaic effect is a kind of second-order nonlinear photoelectric response, which means that the photocurrent generated varies with the polarization angle of circularly polarized light. The generation of photocurrent depends on many factors such as spin, valley polarization, symmetry and Berry curvature, so it can reveal the fundamental physical properties of materials. In this review, we discuss the main mechanisms of circularly polarized photovoltaic effect in different material systems, including circularly polarized optical current caused by symmetry breakdown of Rashba spin-orbit coupling in semiconductor heterojunction, the electron momentum selection caused by Berry curvature and Pauli blocking in topological Weyl semimetals, and the valley polarization current generated by circularly polarized light in TMDC. Additionally, the recent progress of applications of circular photogalvanic effect is also presented.
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图 6 TaIrTe的[41] (a) 光电流响应, 1/4波片快轴与入射光偏振方向的夹角为自变量; (b) 从
$\hat{\theta }$ 空间到角频率空间的傅里叶变换; (c) 10.6和 4.0 μm激发下光电流$ {I}_{1/\mathrm{\pi }} $ 的功率依赖; (d) 动量空间中一对Weyl锥的手性选择规则和CPGE响应示意图. 灰虚线表示未施加内置电场的费米能级μ, 红色十字标志着禁止的跃迁 -
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