Anisotropic Fermi Contour of (001) GaAs Electrons in Parallel Magnetic Fields

TL;DR

This study reveals how a parallel magnetic field causes significant anisotropy in the Fermi contour of high-mobility electrons in a GaAs quantum well, using experimental techniques and theoretical calculations.

Contribution

It provides the first direct experimental measurement of Fermi contour anisotropy induced by parallel magnetic fields in GaAs electrons, and compares results with theoretical models.

Findings

Fermi contour becomes highly anisotropic under parallel magnetic field

Experimental measurements semi-quantitatively match theoretical calculations

Discrepancies suggest need for refined models or additional effects

Abstract

We demonstrate a severe Fermi contour anisotropy induced by the application of a parallel magnetic field to high-mobility electrons confined to a 30-nm-wide (001) GaAs quantum well. We study commensurability oscillations, namely geometrical resonances of the electron orbits with a unidirectional, surface-strain-induced, periodic potential modulation, to directly probe the size of the Fermi contours along and perpendicular to the parallel field. Their areas are obtained from the Shubnikov-de Haas oscillations. Our experimental data agree semi-quantitatively with the results of parameter-free calculations of the Fermi contours but there are significant discrepancies.