Motor effect in electron transport through a molecular junction with torsional vibrations

TL;DR

This paper models a molecular junction with torsional vibrations, revealing how voltage can control angular momentum, leading to a molecular motor behavior with negative differential conductance.

Contribution

It introduces a novel model linking torsional vibrations and electron transport, demonstrating voltage-controlled angular momentum and motor-like function in molecular junctions.

Findings

Negative differential conductance observed in I-V characteristics.

Voltage controls the angular momentum of the junction.

Vibrationally dependent coupling enhances motor behavior.

Abstract

We propose a model for a molecular junction with internal anharmonic torsional vibrations interacting with an electric current. The Wangsness-Bloch-Redfield master equation approach is used to determine the stationary reduced density matrix of the molecule. The dependence of the current, excitation energy and angular momentum of the junction on the applied voltage is studied. Negative differential conductance is observed in the current-voltage characteristics. It is shown that a model with vibrationally dependent coupling to the electrodes, asymmetric with respect to the interchanging of electrodes, leads to a strong correlation between the applied voltage and the angular momentum of the junction. The model thus works as a molecular motor, with the angular momentum controlled by the size and sign of the voltage.