Circular Photogalvanic Effect in Complex Solids from First Principles

The circular photogalvanic effect (CPGE) refers to the photocurrents generated by circularly-polarized light in non-centrosymmetric bulk systems without the need of external bias or inhomogeneous doping. This is an important technique that characterizes topological properties, symmetry and spin textures, and is closely related to light-induced spin-polarized current generation. In insulators, CPGE results from inter-band transitions while in metallic systems both inter-band and intra-band processes can contribute. We present methods to calculate inter-band CPGE and intra-band Berry curvature dipole contributions directly from density functional theory (DFT) using a finite difference method in reciprocal space, without the need for Wannier interpolation or sum over empty states. This reduces the computational cost and eliminates possible systematic errors from the construction of Wannier functions. We demonstrate the flexibility of our method to calculate CPGE in a variety of semimetals and insulators, including two-dimensional (2D) Perovskite NPB and chiral RhSi. With our method, we reproduce previous model predictions of quantized CPGE at low excitation energies for RhSi from first principles. We then present our predictions for a large complex perovskite system, 2D-NPB, where we investigate the angle dependence between the light propagation and current collection directions, as well as the contributions from the organic and inorganic components of the 2D perovskite, which provides the important mechanistic insights for enhancing CPGE in such materials.