Charge-memory effect in a polaron model: equation-of-motion method for Green functions

TL;DR

This paper investigates charge-memory effects in a polaron model of a single-molecule junction, using an equation-of-motion Green function approach to reveal bistability and hysteresis under voltage control.

Contribution

It introduces and evaluates truncation schemes for non-equilibrium Green functions in a polaron model, highlighting charge-bistability and hysteresis phenomena.

Findings

Charge-bistability observed under gate or bias voltage.

Hysteretic behavior indicates potential for charge-memory applications.

System parameters influence the stability and bistability regions.

Abstract

We analyze a single-level quantum system placed between metallic leads and strongly coupled to a localized vibrational mode, which models a singlemolecule junction or an STM setup. We consider a polaron model describing the interaction between electronic and vibronic degrees of freedom and develop and examine different truncation schemes in the equation-of-motion method within the framework of non-equilibrium Green functions. We show that upon applying gate or bias voltage, it is possible to observe charge-bistability and hysteretic behavior which can be the basis of a charge-memory element. We further perform a systematic analysis of the bistability behaviour of the system for different internal parameters such as the electron-vibron and the lead-molecule coupling strength.