Gate tunable circular photogalvanic effect at amorphous-LaAlO3/SrTiO3 interfaces

Interface electronic states at perovskite oxide interfaces represent an important class of heterostructures that exhibit a wide range of functional properties. The circular photogalvanic effect (CPGE), which originates from microscopic inversion symmetry breaking and the resulting spin-orbit coupling, is a significant phenomenon observed in this system. In this study, we investigated the CPGE at amorphous-LaAlO₃/ SrTiO₃ (a-LAO/STO) interfaces under 450 nm, 532 nm, and 780 nm illumination. The CPGE photocurrent demonstrates gate-tunable characteristics, showing linear dependence on back-gate voltage ( V G ) and exhibiting polarity reversal under negative V G . These effects arise from illumination-driven migration of oxygen vacancies and electrons. Under negative V G , the migration induces reversed asymmetry distribution of oxygen vacancies and electrons, leading to photocurrent direction reversal. The opposite migration of oxygen vacancies and electrons expands the width of photon-absorbing region, producing the observed linear V G dependence.