The inelastic relaxation time due to electron-electron collisions in high-mobility two-dimensional systems under microwave radiations

TL;DR

This paper challenges previous assumptions about the inelastic relaxation time in high-mobility 2D systems under microwave radiation, showing that nonequilibrium electron distributions significantly alter the estimated relaxation times.

Contribution

It demonstrates that using nonequilibrium distribution functions instead of equilibrium ones leads to a different understanding of relaxation times under microwave irradiation.

Findings

The inelastic relaxation time is much shorter under microwave radiation than previously thought.

Models assuming large inelastic relaxation times may not be valid in irradiated high-mobility 2D systems.

Electron distribution functions deviate significantly from equilibrium under microwave irradiation.

Abstract

In some theoretical analyses of microwave-induced magnetoresistance oscillations in high-mobility two-dimensional systems, the "inelastic relaxation time" $\tau_{in}$ due to electron-electron scattering is evaluated using an equilibrium distribution function $f^0$ in the absence of radiation, and it is concluded that $\tau_{in}$ is much larger than $\tau_{q}$, the single-particle relaxation time due to impurity scattering. However, under the irradiation of a microwave capable of producing magnetoresistance oscillation, the distribution function of the high-mobility electron gas deviates remarkably from $f^0$ at low temperatures. Estimating $\tau_{in}$ using an approximate nonequilibrium distribution function rather than using $f^0$, one will find the system to be in the opposite limit $1/\tau_{in}\ll 1/\tau_{q}$ even for T=0 K. Therefore, models which depend on the assumption $1/\tau_{in}\gg 1/\tau_{q}$ may not be justifiable.