Impact ionization processes in a photodriven Mott insulator: influence of phononic dissipation

TL;DR

This study models a Mott insulator photovoltaic system with phonons, revealing impact ionization peaks in photocurrent affected by hybridization and phononic dissipation, using nonequilibrium DMFT.

Contribution

It introduces a nonequilibrium DMFT approach including phonons to analyze impact ionization in a driven Mott insulator photovoltaic device.

Findings

Photocurrent peaks at specific frequencies linked to impact ionization.

Hybridization influences the prominence of impact ionization effects.

Acoustic phonons slightly enhance or suppress photocurrent depending on frequency.

Abstract

We study a model for photovoltaic energy collection consisting of a Mott insulating layer in presence of acoustic phonons, coupled to two wide-band fermion leads at different chemical potentials and driven into a nonequilibrium steady state by a periodic electric field. We treat electron correlations with nonequilibrium dynamical mean-field theory (DMFT) using the so-called auxiliary master equation approach as impurity solver and include dissipation by acoustic phonons via the Migdal approximation. For a small hybridization to the leads, we obtain a peak in the photocurrent as a function of the driving frequency which can be associated with impact ionization processes. For larger hybridizations the shallow peak suggests a suppression of impact ionization with respect to direct photovoltaic excitations. Acoustic phonons slightly enhance the photocurrent for small driving frequencies and suppress it at frequencies around the main peak at all considered hybridization strengths.