Robust negative differential conductance and enhanced shot noise in transport through a molecular transistor with vibration assistance

TL;DR

This study investigates vibration-assisted electron transport in a molecular quantum dot, revealing conditions for negative differential conductance and super-Poissonian noise, with implications for molecular electronics.

Contribution

It introduces a model analyzing vibration-assisted tunneling with asymmetric phonon coupling, highlighting the emergence of negative differential conductance and shot noise enhancement.

Findings

Strong negative differential conductance observed with asymmetric phonon coupling.

Super-Poissonian shot noise occurs under certain vibrational conditions.

Conditions for negative differential conductance are thoroughly discussed.

Abstract

In this paper, we analyze vibration-assisted sequential tunneling (including current-voltage characteristics and zero-frequency shot noise) through a molecular quantum dot with two electronic orbitals asymmetrically coupled to the internal vibration. We employ rate equations for the case of equilibrated phonons, and strong Coulomb blockade. We find that a system with a strongly phonon-coupled ground state orbital and weakly phonon-coupled excited state orbital exhibits strong negative differential conductance; and it also shows super-Poissonian current noise. We discuss in detail the reasons and conditions for the appearance of negative differential conductance.