Interaction-induced negative differential resistance in asymmetric molecular junctions

TL;DR

This paper presents a mechanism for negative differential resistance in asymmetric molecular junctions, caused by orbital asymmetry and electron interactions, with potential for molecular device design.

Contribution

It introduces a novel explanation for NDR in weakly coupled molecular junctions based on orbital asymmetry and electron-electron interactions, supported by quantum chemistry and master equations.

Findings

NDR arises from orbital asymmetry and electron interactions.

Asymmetry can be engineered via molecular functionalization.

The mechanism explains NDR in specific molecular configurations.

Abstract

Combining insights from quantum chemistry calculations with master equations, we discuss a mechanism for negative differential resistance (NDR) in molecular junctions, operated in the regime of weak tunnel coupling. The NDR originates from an interplay of orbital spatial asymmetry and strong electron-electron interaction, which causes the molecule to become trapped in a non-conducting state above a voltage threshold. We show how the desired asymmetry can be selectively introduced in individual orbitals in e.g., OPE-type molecules by functionalization with a suitable side group, which is in linear conjugation to one end of the molecule and cross-conjugated to the other end.