Dynamical symmetry breaking in transport through molecules

TL;DR

This paper investigates how vibrational and electronic interactions in molecules cause a dynamical symmetry breaking, resulting in asymmetric current behavior in molecular transistors due to quasi-degenerate vibrational states.

Contribution

It introduces the concept of dynamical symmetry breaking in molecular transport caused by vibrational-electronic interplay and environmental effects.

Findings

Quasi-degenerate vibrational states lead to occupation imbalance.

Dynamical symmetry breaking causes current asymmetry.

Thermal environment and tunneling induce state occupation differences.

Abstract

We analyze the interplay between vibrational and electronic degrees of freedom in charge transport across a molecular single-electron transistor. We focus on the wide class of molecules which possess quasi-degenerate vibrational eigenstates, while no degeneracy occurs for their anionic configuration. We show that the combined effect of a thermal environment and coupling to leads, involving tunneling events charging and discharging the molecule, leads to a dynamical symmetry breaking where quasi-degenerate eigenstates acquire different occupations. This imbalance gives rise to a characteristic asymmetry of the current versus an applied gate voltage.