Fig. 1: Bulk photovoltaic effect and microscopic picture.
From: Pure bulk orbital and spin photocurrent in two-dimensional ferroelectric materials
a Schematic plot of bulk angular momentum photoconductivity (BOPV and BSPV) effect. Unlike BPV that propagates along the mirror plane of monolayer GeS, the BOPV and BSPV currents carrying orbital and spin DOF information are traveling normal to the mirror plane (\({\cal{M}}_x\)) under light. A four-terminal device can be used to detect all these photocurrents. The yellow electrode measures charge DOF, while the blue electrodes are magnetic and could measure angular momentum DOF. b Interband transition (pink arrows) picture, where black arrows indicate angular momentum or magnetic moment from orbital and spin DOF. Solid and dashed curves represent occupied (valence) and unoccupied (conduction) bands of the semiconductor, respectively.
