Ballistic photocurrent driven by optical phonon modes in a polaronic ferroelectric

We investigate the effect of local electron-phonon coupling on nonlinear optical conductivity in an interacting ferroelectric system. Using real-time simulations, we show an enhancement in nonlinear conductivity under linearly polarized light due to generation of the phonon-assisted ballistic current in addition to the injection current generated by electron-hole pairs. The optically excited phonon modes generate an asymmetric carrier distribution that causes a strong directional ballistic current. The ballistic current enhances the photocurrent several times at above band-gap excitation frequencies and is sublinearly dependent on the excitation intensity. This strong phonon-assisted zero-frequency directional ballistic current demonstrates an alternative way to boost the bulk photovoltaic effect (BPVE) in electronic ferroelectric materials with strong local electron-phonon coupling.

Automated summary

We investigated the impact of local electron-phonon coupling on the nonlinear optical conductivity in a ferroelectric system. Our real-time simulations revealed that under linearly polarized light, there is an increase in nonlinear conductivity due to the generation of phonon-assisted ballistic current alongside the injection current created by electron-hole pairs. The optically excited phonon modes result in an asymmetric carrier distribution, leading to a strong directional ballistic current. This ballistic current enhances the photocurrent multiple times at frequencies higher than the band gap, and its dependence on the excitation intensity is sublinear. This study demonstrates an alternative method to enhance the bulk photovoltaic effect (BPVE) in electronically ferroelectric materials with strong local electron-phonon coupling.