Quantum oscillation of the circular photogalvanic effect in Weyl semimetals under strong magnetic fields

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. © 2024 American Physical Society.