Current collapse in tunneling transport through benzene

TL;DR

This paper models electron tunneling through benzene molecules connected to electrodes, predicting current collapse and negative differential conductance due to specific molecular states and coupling positions.

Contribution

It introduces a semi-quantitative model including two-body interactions and predicts novel transport phenomena like current collapse and negative differential conductance.

Findings

Current collapse occurs at para-position coupling.

Negative differential conductance is observed due to a blocking state.

Meta-position coupling shows step-like I-V characteristics.

Abstract

We investigate the electrical transport through a system of benzene coupled to metal electrodes by electron tunneling. Using electronic structure calculations, a semi--quantitative model for the pi-electrons of the benzene is derived that includes general two-body interactions. After exact diagonalization of the benzene model the transport is computed using perturbation theory for weak electrode-benzene coupling (golden rule approximation). We include the effect of an applied electric field on the molecular states, as well as radiative relaxation. We predict a current collapse and strong negative differential conductance due to a ``blocking'' state when the electrode is coupled to the para-position of benzene. In contrast, for coupling to the meta-position, a series of steps in the I-V curve is found.