Heat conduction in molecular transport junctions

TL;DR

This paper develops a comprehensive NEGF-based framework to analyze heat conduction in molecular junctions, addressing electron and phonon contributions, their interplay, and introducing a novel method to measure local temperature in nonequilibrium conditions.

Contribution

It provides a unified NEGF formalism for heating and heat conduction in molecular junctions, including a new technique for defining local temperature in nonequilibrium systems.

Findings

New NEGF-based description of heating in molecular junctions

Introduction of a novel local temperature measurement method

Numerical examples demonstrating the approach's effectiveness

Abstract

Heating and heat conduction in molecular junctions are considered within a general NEGF formalism. We obtain a unified description of heating in current carrying molecular junctions as well as the electron and phonon contributions to the thermal flux, including their mutual influence. Ways to calculate these contributions, their relative importance and ambiguities in their definitions are discussed. A general expression for the phonon thermal flux is derived and used in a new "measuring technique", to define and quantify 'local temperature' in nonequilibrium systems. Superiority of this measuring technique over the usual approach that defines effective temperature using the equilibrium phonon distribution is demonstrated. Simple bridge models are used to illustrate the general approach, with numerical examples.