Energy transfer between two vacuum-gapped metal plates: Coulomb fluctuation and electron tunneling

TL;DR

This paper investigates energy transfer mechanisms between two vacuum-gapped metal plates at nanometer scales, focusing on Coulomb fluctuations and electron tunneling, using advanced theoretical methods to analyze the crossover region.

Contribution

It introduces a nonequilibrium Green's function approach to unify Coulomb fluctuation and electron tunneling contributions in near-field heat transfer models.

Findings

Caroli formula derived from Meir-Wingreen formula matches fluctuational electrodynamics.

The study characterizes the crossover from electron tunneling to Coulomb fluctuation.

Numerical results reveal the dominant energy transfer mechanism at different gap distances.

Abstract

Recent experimental measurements for near-field radiative heat transfer between two bodies have been able to approach the gap distance within $2 \; \textrm{nm}$, where the contributions of Coulomb fluctuation and electron's tunneling are comparable. Using the nonequilibrium Green's function method in the $G_{0}W_{0}$ approximation, based on a tight-binding model, we obtain for the energy current a Caroli formula from the Meir-Wingreen formula in the local equilibrium approximation. Also, the Caroli formula is consistent with the evanescent part of the heat transfer from the theory of fluctuational electrodynamics. We go beyond the local equilibrium approximation to study the energy transfer in the crossover region from electron tunneling to Coulomb fluctuation based on a numerical calculation.