  Solid systems with strong correlations and interactions under light
illumination have the potential for exhibiting interesting bulk photovoltaic
behavior in the non-perturbative regime, which has remained largely unexplored
in the past theoretical studies. We investigate the bulk photovoltaic response
of a perovskite manganite with strongly coupled electron-spin-lattice dynamics,
using real-time simulations performed with a tight-binding model. 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. The predicted peak
photoresponsivity is orders of magnitude higher than other known ferroelectric
oxides such as BiFeO$_3$. We disentangle phonon-and spin-assisted components to
the ballistic photocurrent, showing that they are comparable in magnitude. Our
results illustrate a promising alternative way for controlling and optimizing
the bulk photovoltaic response through the photoinduced phase transitions in
strongly-correlated systems.
