Non-linear response of molecular junctions: The polaron model revisited

TL;DR

This paper revisits the polaron model to analyze nonlinear conductance in molecular junctions, highlighting differences between weak and strong coupling regimes and providing approximate Green function expressions for inelastic transport.

Contribution

It offers a new approximate Green function expression for inelastic transport in molecular junctions, bridging isolated molecule and static vibration limits.

Findings

Derived an approximate Green function for inelastic transport.

Clarified the relevance of isolated molecule limits to junction properties.

Analyzed differences between weak and strong molecule-lead coupling.

Abstract

A polaron model proposed as a possible mechanism for nonlinear conductance [Galperin M, Ratner M A, and Nitzan A 2005 Nano Lett. 5 125-30] is revisited with focus on the differences between the weak and strong molecule-lead coupling cases. Within the one-molecular level model we present an approximate expression for the electronic Green function corresponding to inelastic transport case, which in the appropriate limits reduces to expressions presented previously for the isolated molecule and for molecular junction coupled to a slow vibration (static limit). The relevance of considerations based on the isolated molecule limit to understanding properties of molecular junctions is discussed.