Real-time switching between multiple steady-states in quantum transport

TL;DR

This paper investigates how many-body interactions influence the existence and switching of multiple steady-states in quantum transport systems, revealing that beyond mean-field approximations, bistability can be suppressed.

Contribution

It demonstrates that advanced self-energy approximations like second Born and GW eliminate bistability seen at the Hartree-Fock level in quantum transport models.

Findings

Multiple steady-states exist at Hartree-Fock level.

Beyond mean-field, only one steady-state is found.

Gate voltage pulses can switch between steady-states at Hartree-Fock.

Abstract

We study transport through an interacting model system consisting of a central correlated site coupled to finite bandwidth tight-binding leads, which are considered as effectively noninteracting. Its nonequilibrium properties are determined by real-time propagation of the Kadanoff-Baym equations after applying a bias voltage to the system. The electronic interactions on the central site are incorporated by means of self-energy approximations at Hartree-Fock, second Born and GW level. We investigate the conditions under which multiple steady-state solutions occur within different self-energy approximations, and analyze in detail the nature of these states from an analysis of their spectral functions. At the Hartree-Fock level at least two stable steady-state solutions with different densities and currents can be found. By applying a gate voltage-pulse at a given time we are able to switch between these solutions. With the same parameters we find only one steady-state solution when the self-consistent second Born and GW approximations are considered. We therefore conclude that treatment of many-body interactions beyond mean-field can destroy bistability and lead to qualitatively different results as compared those at mean-field level.