Measurements of the density-dependent many-body electron mass in 2D GaAs/AlGaAs Heterostructures

TL;DR

This study measures how the effective electron mass in 2D GaAs/AlGaAs heterostructures varies with electron density, revealing a significant increase at low densities and providing experimental data to compare with theoretical models.

Contribution

The paper provides detailed experimental measurements of the density-dependent electron mass in 2D GaAs/AlGaAs systems over a wide density range, highlighting the mass enhancement at low densities.

Findings

Electron mass increases by up to 40% at low densities.

Mass values are about 10% below the band mass at higher densities.

Qualitative agreement with numerical calculations, but with notable differences.

Abstract

We determine the density-dependent electron mass, m*, in two-dimensional (2D) electron systems of GaAs/AlGaAs heterostructures by performing detailed low-temperature Shubnikov deHaas measurements. Using very high quality transistors with tunable electron densities we measure m* in single, high mobility specimens over a wide range of r_s (6 to 0.8). Toward low-densities we observe a rapid increase of m* by as much as 40%. For 2>r_s>0.8 the mass values fall ~10% below the band mass of GaAs. Numerical calculations are in qualitative agreement with our data but differ considerably in detail.