Nonequilibrium Green's-Function Approach to the Suppression of Rectification at Metal--Mott-Insulator Interfaces

TL;DR

This paper uses nonequilibrium Green's functions to theoretically analyze why rectification is suppressed at metal--Mott-insulator interfaces, revealing collective charge transport as the key factor.

Contribution

It introduces a Green's function approach to explain rectification suppression, incorporating electrode effects and a scalar potential in a Mott insulator model.

Findings

Charge transport is collective in Mott insulators.

Rectification suppression is due to extended electron-hole states.

Electrode effects and potential differences influence charge dynamics.

Abstract

Suppression of rectification at metal--Mott-insulator interfaces, which is previously shown by numerical solutions to the time-dependent Schr\"odinger equation and experiments on real devices, is reinvestigated theoretically by nonequilibrium Green's functions. The one-dimensional Hubbard model is used for a Mott insulator. The effects of attached metallic electrodes are incorporated into the self-energy. A scalar potential originating from work-function differences and satisfying the Poisson equation is added to the model. For the electron density, we decompose it into three parts. One is obtained by integrating the local density of states over energy to the midpoint of the electrodes' chemical potentials. The others, obtained by integrating lesser Green's functions, are due to the couplings with the electrodes and correspond to an inflow and an outflow of electrons. In Mott insulators, incoming electrons and holes are extended over the whole system, avoiding further accumulation of charge relative to the case without bias. This induces collective charge transport and results in the suppression of rectification.