Theory of electron-phonon interaction in a nonequilibrium open electronic system

TL;DR

This paper investigates how a steady nonequilibrium voltage affects electron-phonon interactions in a 2D electron gas, revealing tunable phonon and screening properties via theoretical analysis using the Keldysh formalism.

Contribution

It introduces a theoretical framework for analyzing nonequilibrium electron-phonon interactions in open 2D systems with voltage bias, highlighting tunable physical properties.

Findings

Voltage modifies electron-phonon scattering rate.

Effective electron mass is affected by nonequilibrium conditions.

Phonon velocity and screening length can be tuned with voltage.

Abstract

We study the effects of time-independent nonequilibrium drive on an open 2D electron gas system coupled to 2D longitudinal acoustic phonons using the Keldysh path integral method. The layer electron-phonon system is defined at the two-dimensional interface between a pair of three-dimensional Fermi liquid leads, which act both as a particle pump and an infinite bath. The nonequilibrium steady state is achieved in the layer by assuming the leads to be thermally equilibrated at two different chemical potentials. This subjects the layer to an out-of-plane voltage $V$ and drives a steady-state charge current perpendicular to the system. We compute the effects of small voltages ($V\ll\w_D$) on the in-plane electron-phonon scattering rate and the electron effective mass at zero temperature. We also find that the obtained onequilibrium modification to the acoustic phonon velocity and the Thomas-Fermi screening length reveal the possibility of tuning these quantities with the external voltage.