Impact ionization processes in the steady state of a driven Mott-insulating layer coupled to metallic leads

Description

We study a simple model of photovoltaic energy harvesting across a Mott insulating gap consisting of a correlated layer connected to two metallic leads held at different chemical potentials. We address in particular the issue of impact ionization, whereby a particle photoexcited to the high-energy part of the upper Hubbard band uses its extra energy to produce a second particle-hole excitation. We find a drastic increase of the photocurrent upon entering the frequency regime where impact ionization is possible.
At large values of the Mott gap, where impact ionization is energetically not allowed, we observe a suppression of the current and a piling up of charge in the high-energy part of the upper Hubbard band.Our study is based on a Floquet dynamical mean field theory treatment of the steady state with the so-called auxiliary master equation approach as impurity solver. We verify that an additional approximation, taking the self-energy diagonal in the Floquet indices, is appropriate
for the parameter range we are considering.

Period	5 Apr 2018
Held at	From Electrons to Phase Transitions 2018
Event type	Conference
Location	Vienna, Austria
Degree of Recognition	International