Conserving approximations in time-dependent quantum transport: Initial correlations and memory effects

TL;DR

This paper investigates how initial correlations and memory effects influence transient and steady-state currents in time-dependent quantum transport using the Kadanoff-Baym equations, highlighting the importance of many-body interactions.

Contribution

It demonstrates the significant impact of initial correlations and memory effects on transient dynamics and steady-state currents in correlated quantum transport models.

Findings

Initial correlations greatly affect transient current behavior.

Memory effects influence the approach to steady state.

Steady state current depends on the approximation of electronic interactions.

Abstract

We study time-dependent quantum transport in a correlated model system by means of time-propagation of the Kadanoff-Baym equations for the nonequilibrium many-body Green function. We consider an initially contacted equilibrium system of a correlated central region coupled to tight-binding leads. Subsequently a time-dependent bias is switched on after which we follow in detail the time-evolution of the system. Important features of the Kadanoff-Baym approach are 1) the possibility of studying the ultrafast dynamics of transients and other time-dependent regimes and 2) the inclusion of exchange and correlation effects in a conserving approximation scheme. We find that initial correlation and memory terms due to many-body interactions have a large effect on the transient currents. Furthermore the value of the steady state current is found to be strongly dependent on the approximation used to treat the electronic interactions.