Spatially probed electron-electron scattering in a two-dimensional electron gas

TL;DR

This study uses scanning gate microscopy to investigate electron-electron scattering in a 2D electron gas, revealing energy-dependent scattering behaviors and a localized non-equilibrium electron distribution near the injection point.

Contribution

It uncovers a novel high-energy scattering effect where back-scattering increases conductance, and characterizes the spatial and energetic extent of non-equilibrium electron distributions.

Findings

Small-angle scattering at low energies

Back-scattering increases conductance at high energies

Non-equilibrium region within ~1 micrometer of injection point

Abstract

Using scanning gate microscopy (SGM), we probe the scattering between a beam of electrons and a two-dimensional electron gas (2DEG) as a function of the beam's injection energy, and distance from the injection point. At low injection energies, we find electrons in the beam scatter by small-angles, as has been previously observed. At high injection energies, we find a surprising result: placing the SGM tip where it back-scatters electrons increases the differential conductance through the system. This effect is explained by a non-equilibrium distribution of electrons in a localized region of 2DEG near the injection point. Our data indicate that the spatial extent of this highly non-equilibrium distribution is within ~1 micrometer of the injection point. We approximate the non-equilibrium region as having an effective temperature that depends linearly upon injection energy.