We develop a quantum theory to investigate nonlinear effects using the lesser Green's function, through which we explore the circular photogalvanic effect (CPGE) in Weyl semimetals (WSMs) under strong magnetic fields. A simple analytical expression is derived for the injection conductivity. It demonstrates that the achiral Landau levels (LLs) can induce a chirality-dependent injection current, because of their topologically nontrivial wave functions. The CPGE in different frequency regions is dominated by distinct physical mechanisms. In the low-frequency regime, the CPGE can be significantly enhanced by magnetic fields, due to the chiral $n=0$ LL. At high frequencies, the injection conductivity saturates to the quantized value observed at zero magnetic field, reflecting the topological nature of the achiral LLs. Upon application of parallel electric and magnetic fields, the CPGE exhibits a quantum oscillation that is periodic in $1/B$. The periodic-in-$1/B$ quantum oscillation of the CPGE in WSMs can serve as a highly sensitive measurement of the chiral anomaly.

中文翻译：

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强磁场下外尔半金属圆形光电效应的量子振荡


我们发展了一种量子理论来研究使用小格林函数的非线性效应，通过它我们探索了强磁场下外尔半金属（WSM）中的圆形光电效应（CPGE）。推导了注入电导率的简单解析表达式。它表明，非手性朗道能级（LL）由于其拓扑非平凡的波函数，可以诱导手性相关的注入电流。不同频率区域的 CPGE 受不同的物理机制支配。在低频区域，由于手性，磁场可以显着增强 CPGE $n=0$ 二。在高频下，注入电导率饱和到零磁场下观察到的量子化值，反映了非手性 LL 的拓扑性质。在应用平行电场和磁场时，CPGE 表现出周期性的量子振荡 $1/B$ 。周期性的 $1/B$ WSM 中 CPGE 的量子振荡可以作为手性异常的高灵敏度测量。