Relaxation of high-energy quasiparticle distributions: electron-electron scattering in a two-dimensional electron gas

TL;DR

This paper develops a theory for how high-energy quasiparticle distributions relax in a 2D electron gas, explaining experimental observations of electron scattering signals related to a transition from ballistic to hydrodynamic flow.

Contribution

It introduces a modified one-collision approximation tailored for high-energy quasiparticles and applies it to interpret novel experimental measurements.

Findings

The theory explains non-monotonic energy dependence of scattered electron signals.

It links observed effects to a crossover from ballistic to hydrodynamic regimes.

The approach provides a new framework for understanding quasiparticle relaxation in 2D systems.

Abstract

A theory is developed for the evolution of the non-equilibrium distribution of quasiparticles when the scattering rate decreases due to particle collisions. We propose a "modified one-collision approximation" which is most effective for high-energy quasiparticle distributions. This method is used to explain novel measurements of the non-monotonic energy dependence of the signal of scattered electrons in a 2D system. The observed effect is related to a crossover from the ballistic to the hydrodynamic regime of electron flow.