Energy-Dependent Electron-Electron Scattering and Spin Dynamics in a Two Dimensional Electron Gas

TL;DR

This study investigates how electron-electron scattering affects spin dynamics in a two-dimensional electron gas, revealing energy-dependent transition from collision-free to collision-dominated regimes near the Fermi energy.

Contribution

It provides the first detailed measurement of energy-dependent electron-electron scattering times in a 2D electron gas using spin dynamics and Monte Carlo simulations.

Findings

Near Fermi energy, spin dynamics are oscillatory, indicating quasi-collision-free behavior.

At higher energies, a transition to exponential decay shows collision-dominated spin relaxation.

Electron-electron scattering time decreases quadratically with energy above the Fermi level.

Abstract

Measurements of spin dynamics of electrons in a degenerate two dimensional electron gas, where the Dyakonov-Perel mechanism is dominant, have been used to investigate the electron scattering time (tp*) as a function of energy near the Fermi energy. Close to the Fermi energy the spin evolution is oscillatory, indicating a quasi-collision-free regime of spin dynamics. As the energy is increased a transition to exponential, collision-dominated, spin decay occurs. The frequency and the value of tp* are extracted using a Monte Carlo simulation method. At the Fermi energy tp* is very close to the ensemble momentum relaxation time (tp) obtained from the electron mobility. For higher energies tp* falls quadratically, consistent with theoretical expectations for the onset of electron-electron scattering which is inhibited by the Pauli principle at the Fermi energy.