  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.
