Effect of scattering and recombination on photocurrent in non-centrosymmetric systems from ab-initio density matrix dynamics*

Uniform illumination of crystals lacking a center of symmetry generates a direct photocurrent. The phenomenon, also referred to as photogalvanic effect, has been intensively investigated both experimentally and theoretically since its discovery in the late 1960s. The interest remains now due to its important impact on bulk photovoltaic applications and nonlinear optics. Although various prior theoretical approaches have made significant progress on its physical understanding, they have been largely limited to model Hamiltonians or perturbative methods with relaxation time approximation. An ab-initio predictive tool including various kinetic processes simultaneously remains to be developed. In this talk, we show, by building on our recent development of a general-purpose ab-initio real-time density-matrix dynamics approach that includes various quantum scattering channels [1] and takes into account the effect of recombinations, the further development of the method for computing transient and steady-state photocurrents. We analyze the nature of the photocurrent under linear and circularly polarized light, and investigate the photocurrent dependence on electron-phonon, electron-electron, electron-impurity scatterings as well as electron-hole recombination, as a function of temperature and doping density in noncentro-symmetric semiconductors and semimetals. Our work can provide the useful physical insights into the dominant mechanism and guide experiments for optimal photocurrents in applications.

[1]  J. Xu, A. Habib, R. Sundararaman, and Y. Ping, Ab initio ultrafast spin dynamics in solids, Phys. Rev. B 104, 184418 (2021).