Adiabaticity in semiclassical nanoelectromechanical systems

TL;DR

This paper investigates the dynamics of nanoelectromechanical systems (NEMS) by comparing adiabatic and non-adiabatic regimes using a semiclassical approach, revealing complex oscillator behavior influenced by electronic current.

Contribution

It introduces a non-perturbative Langevin equation for NEMS that captures the effects of system-leads coupling beyond the adiabatic approximation.

Findings

Oscillator exhibits nontrivial dynamics driven by electronic current.

Differences between adiabatic and non-adiabatic regimes are analyzed for systems with one and two electronic levels.

Backaction effects of the oscillator on the electronic current are characterized.

Abstract

We compare the semiclassical description of NEMS within and beyond the adiabatic approximation. We consider a NEMS model which contains a single phonon (oscillator) mode linearly coupled to an electronic few-level system in contact with external particle reservoirs (leads). Using Feynman-Vernon influence functional theory, we derive a Langevin equation for the oscillator trajectory that is non-perturbative in the system-leads coupling. A stationary electronic current through the system generates nontrivial dynamical behavior of the oscillator, even in the adiabatic regime. The 'backaction' of the oscillator onto the current is studied as well. For the two simplest cases of one and two coupled electronic levels, we discuss the differences between the adiabatic and the non-adiabatic regime of the oscillator dynamics.