Vibrational Instabilities in Resonant Electron Transport through Single-Molecule Junctions

TL;DR

This paper investigates vibrational instabilities in single-molecule junctions during resonant electron transport, revealing conditions under which vibrational excitation diverges and linking these instabilities to electron-hole pair creation.

Contribution

The study provides analytic and numerical insights into vibrational instabilities in molecular junctions under high bias or weak coupling, highlighting their relation to electron-hole pair processes.

Findings

Vibrational excitation increases indefinitely under certain conditions.

Analytic expressions for vibrational distribution functions are derived.

Vibrational instabilities are connected to electron-hole pair creation processes.

Abstract

We analyze various limits of vibrationally coupled resonant electron transport in single-molecule junctions. Based on a master equation approach, we discuss analytic and numerical results for junctions under a high bias voltage or weak electronic-vibrational coupling. It is shown that in these limits the vibrational excitation of the molecular bridge increases indefinitely, i.e. the junction exhibits a vibrational instability. Moreover, our analysis provides analytic results for the vibrational distribution function and reveals that these vibrational instabilities are related to electron-hole pair creation processes.