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

We study the effects of time-independent nonequilibrium drive on an open two-dimensional (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 <omega(D)) on the in-plane electron-phonon scattering rate and the electron effective mass at zero temperature. We also find that the obtained nonequilibrium modification to the acoustic phonon velocity and the Thomas-Fermi screening length reveal the possibility of tuning these quantities with the external voltage.