Bulk Photovoltaic Effect Driven by Collective Excitations in a Correlated Insulator

TL;DR

This paper demonstrates that collective electronic excitations in a correlated insulator significantly enhance the bulk photovoltaic effect, revealing new nonlinear optical phenomena driven by electronic correlations.

Contribution

It shows how correlation-driven electronic ferroelectricity can lead to large photovoltaic responses, including resonant and broadband enhancements, which are absent in conventional insulators.

Findings

Enhanced photovoltaic effect due to collective modes

Resonant enhancement at sub-band-gap frequencies

Injection current contribution from deformable electronic order

Abstract

We investigate the bulk photovoltaic effect, which rectifies light into electric current, in a collective quantum state with correlation driven electronic ferroelectricity. We show via explicit real-time dynamical calculations that the effect of the applied electric field on the electronic order parameter leads to a strong enhancement of the bulk photovoltaic effect relative to the values obtained in a conventional insulator. The enhancements include both resonant enhancements at sub-band-gap frequencies, arising from excitation of optically active collective modes, and broadband enhancements arising from nonresonant deformations of the electronic order. The deformable electronic order parameter produces an injection current contribution to the bulk photovoltaic effect that is entirely absent in a rigid-band approximation to a time-reversal symmetric material. Our findings establish that correlation effects can lead to the bulk photovoltaic effect and demonstrate that the collective behavior of ordered states can yield large nonlinear optical responses.