Origin of negative differential resistance in a strongly coupled single molecule-metal junction device

TL;DR

This paper introduces a new quantum transport model explaining negative differential resistance in strongly coupled single molecule-metal junctions, based on wavefunction symmetry breaking and orbital mixing observed in first-principles calculations.

Contribution

It proposes a novel mechanism involving wavefunction symmetry breaking and orbital mixing to explain NDR in molecule-metal junctions, supported by first-principles calculations.

Findings

Emergence of a new phase in the wavefunction with bias increase

Non-linear change in molecule-lead coupling leads to NDR

Model applicable to other metal-molecule junctions

Abstract

A new mechanism is proposed to explain the origin of negative differential resistance (NDR) in a strongly coupled single molecule-metal junction. A first-principles quantum transport calculation in a Fe-terpyridine linker molecule sandwiched between a pair of gold electrodes is presented. Upon increasing applied bias, it is found that a new phase in the broken symmetry wavefunction of the molecule emerges from the mixing of occupied and unoccupied molecular orbital. As a consequence, a non-linear change in the coupling between molecule and lead is evolved resulting to NDR. This model can be used to explain NDR in other class of metal-molecule junction device.