Control and enhancement of the anomalous linear photogalvanic effect for topological optoelectronics

The anomalous linear photogalvanic effect (ALPGE), stemming from inhomogeneous optical excitation under Gaussian laser illumination, enables new possibilities for photodetection and polarization-sensitive optoelectronics. However, clear separation of ALPGE from linear photogalvanic effect (LPGE) in 3D topological insulators and a coherent picture of its behavior under varying thickness, bias, angle, and temperature have been lacking. This work proposes a method to distinguish the ALPGE from the LPGE in Bi2Te3 thin films, based on their distinct dependencies on the incident angle. It is revealed that ALPGE depends oddly on incident angle while maintaining a spot-position-independent peak-to-peak amplitude, diminishes with increasing film thickness from 3 to 10 nm, and exhibits mixed odd and even symmetry under applied bias. Notably, low-temperature measurements reveal a universal enhancement of ALPGE, reaching a fivefold magnitude in 3 nm films, due to the surface-bulk decoupling at low temperature. These findings establish a mechanistic understanding of ALPGE modulation and support its application in topological optoelectronics.