Nonperturbative study of bulk photovoltaic effect enhanced by an optically induced phase transition

Solid systems with strong correlations and interactions under light illumination have the potential for exhibiting interesting bulk photovoltaic behavior in the nonperturbative regime, which has remained largely unexplored in past theoretical studies. We investigate the bulk photovoltaic response of a quantum material with strongly coupled electron-spin-lattice dynamics using real-time simulations performed with a tight-binding model. We demonstrate how a combination of spin- and phonon-induced processes can substantially enhance the bulk photovoltaic effect. The transient changes in the band structure and the photoinduced phase transitions, emerging from spin and phonon dynamics, result in a nonlinear current versus intensity behavior beyond the perturbative limit. The current rises sharply across a photoinduced magnetic phase transition, which later saturates at higher light intensities due to excited phonon and spin modes. We disentangle phonon-and spin-assisted components to the ballistic photocurrent, showing that they are comparable in magnitude. Our study shows that photoinduced phase transitions, which are generally ignored in perturbative theoretical methods, significantly impact photocurrent generation and its evolution. Moreover, understanding the effect of the transient spin and lattice dynamics on the dynamical nature of the band structure can be exploited for desirable photovoltaic properties by tuning the correlations and interactions in correlated systems through targeted materials design.