Effective Mass and Spin Susceptibility of Dilute Two-Dimensional Holes in GaAs

TL;DR

This study measures the effective mass and spin susceptibility of dilute 2D holes in GaAs, finding good agreement with band calculations for mass and a moderate enhancement in spin susceptibility.

Contribution

It provides experimental measurements of hole effective mass and spin susceptibility in dilute 2D GaAs systems, including effects of strong parallel magnetic fields.

Findings

Measured hole effective mass ~0.2, consistent with band calculations.

Observed spin susceptibility enhanced by about 50% over band predictions.

Effective mass remains similar under full spin polarization induced by magnetic field.

Abstract

We report effective hole mass ($m^{*}$) measurements through analyzing the temperature dependence of Shubnikov-de Haas oscillations in dilute (density $p \sim 7 \times 10^{10}$ cm$^{-2}$, $r_{s} \sim 6$) two-dimensional (2D) hole systems confined to a 20 nm-wide, (311)A GaAs quantum well. The holes in this system occupy two nearly-degenerate spin subbands whose $m^{*}$ we measure to be $\sim $ 0.2 (in units of the free electron mass). Despite the relatively large $r_{s}$ in our 2D system, the measured $m^{*}$ is in good agreement with the results of our energy band calculations which do not take interactions into account. We hen apply a sufficiently strong parallel magnetic field to fully depopulate one of the spin subbands, and measure $m^{*}$ for the populated subband. We find that this latter $m^{*}$ is surprisingly close to the $m^{*}$ we measure in the absence of the parallel field. We also deduce the spin susceptibility of the 2D hole system from the depopulation field, and conclude that the susceptibility is enhanced by about 50% relative to the value expected from the band calculations.