Vibration induced memory effects and switching in ac-driven molecular nanojunctions

TL;DR

This paper explores how vibrational effects induce bistability and memory in molecular junctions under AC bias, revealing hysteresis and switching behavior influenced by electron-vibron interactions and vibronic states.

Contribution

It introduces a model analyzing vibrationally induced bistability and hysteresis in molecular junctions with time-dependent bias, emphasizing the role of excited vibronic states in switching dynamics.

Findings

Hysteretic behavior in vibronic state occupation probabilities.

Voltage-driven switching influenced by vibronic states.

Transport properties affected by driving frequency and bias conditions.

Abstract

We investigate bistability and memory effects in a molecular junction weakly coupled to metallic leads with the latter being subject to an adiabatic periodic change of the bias voltage. The system is described by a simple Anderson-Holstein model and its dynamics is calculated via a master equation approach. The controlled electrical switching between the many-body states of the system is achieved due to polaron shift and Franck-Condon blockade in the presence of strong electron-vibron interaction. Particular emphasis is given to the role played by the excited vibronic states in the bistability and hysteretic switching dynamics as a function of the voltage sweeping rates. In general, both the occupation probabilities of the vibronic states and the associated vibron energy show hysteretic behaviour for driving frequencies in a range set by the minimum and maximum lifetimes of the system. The consequences on the transport properties for various driving frequencies and in the limit of DC-bias are also investigated.