Heating in current carrying molecular junctions

TL;DR

This paper presents a framework combining quantum and classical models to estimate heating effects in molecular junctions, finding modest temperature rises but noting potential underestimation by classical heat conduction assumptions.

Contribution

It extends a previous quantum model to evaluate heat generation and temperature rise in molecular junctions, integrating classical heat conduction theory.

Findings

Temperature rise is estimated to be a few degrees for typical junction currents.

Classical heat conduction may underestimate actual heating effects.

The model provides a basis for understanding thermal effects in molecular electronics.

Abstract

A framework for estimating heating and expected temperature rise in current carrying molecular junctions is described. Our approach is based on applying the Redfield approximation to a tight binding model for the molecular bridge supplemented by coupling to a phonon bath. This model, used previously to study thermal relaxation effects on electron transfer and conduction in molecular junctions, is extended and used to evaluate the fraction of available energy, i.e. of the potential drop, that is released as heat on the molecular bridge. Classical heat conduction theory is then applied to estimate the expected temperature rise. For a reasonable choice of molecular parameters and for junctions carrying currents in the nA range, we find the temperature rise to be a modest few degrees. It is argued, however, that using classical theory to describe heat transport away from the junction may underestimate the heating effect.