Molecular junctions and molecular motors: Including Coulomb repulsion in electronic friction using nonequilibrium Green's functions

TL;DR

This paper develops a first-principles theoretical framework combining nonequilibrium Green's functions and Ehrenfest dynamics to study electron-electron interactions in molecular motors, revealing significant effects of correlations on motor behavior.

Contribution

It introduces a systematic method to include Coulomb repulsion in electronic friction calculations for molecular junctions using nonequilibrium Green's functions.

Findings

Correlations can induce sizable damping in molecular motor oscillations.

The method shows excellent agreement with real-time Kadanoff-Baym simulations.

Electron-electron interactions significantly alter the physical behavior of molecular motors.

Abstract

We present a theory of molecular motors based on the Ehrenfest dynamics for the nuclear coordinates and the adiabatic limit of the Kadanoff-Baym equations for the current-induced forces. Electron-electron interactions can be systematically included through many-body perturbation theory, making the nonequilibrium Green's functions formulation suitable for first-principles treatments of realistic junctions. The method is benchmarked against simulations via real-time Kadanoff-Baym equations, finding an excellent agreement. Results on a paradigmatic model of molecular motor show that correlations can change dramatically the physical scenario by, e.g. introducing a sizable damping in the self-sustained van der Pol oscillations.