Transport Through a Correlated Interface: Auxiliary Master Equation Approach

TL;DR

This paper enhances a numerical method to accurately compute steady state properties of strongly correlated electronic systems out of equilibrium, enabling better analysis of phenomena like the Kondo effect and spectral functions under bias.

Contribution

The authors improve the auxiliary master equation approach, allowing larger bath sizes and more accurate non-equilibrium DMFT calculations for correlated systems.

Findings

Observation of Kondo-like behavior near the insulating phase at low bias.

Splitting of the Kondo resonance as bias voltage increases.

Improved spectral function and current-voltage characteristics in strongly correlated regimes.

Abstract

We present improvements of a recently introduced numerical method [Arrigoni etal, Phys. Rev. Lett. 110, 086403 (2013)] to compute steady state properties of strongly correlated electronic systems out of equilibrium. The method can be considered as a non-equilibrium generalization of exact diagonalization based dynamical mean-field theory (DMFT). The key modification for the non-equilibrium situation consists in addressing the DMFT impurity problem within an auxiliary system consisting of the correlated impurity, $N_b$ uncorrelated bath sites and two Markovian environments (sink and reservoir). Algorithmic improvements in the impurity solver allow to treat efficiently larger values of $N_b$ than previously in DMFT. This increases the accuracy of the results and is crucial for a correct description of the physical behavior of the system in the relevant parameter range including a semi-quantitative description of the Kondo regime. To illustrate the approach we consider a monoatomic layer of correlated orbitals, described by the single-band Hubbard model, attached to two metallic leads. The non-equilibrium situation is driven by a bias-voltage applied to the leads. For this system, we investigate the spectral function and the steady state current-voltage characteristics in the weakly as well as in the strongly interacting limit. In particular we investigate the non-equilibrium behavior of quasi-particle excitations within the Mott gap of the correlated layer. We find for low bias voltage Kondo like behavior in the vicinity of the insulating phase. In particular we observe a splitting of the Kondo resonance as a function of the bias voltage.