Effective mass suppression in dilute, spin-polarized two-dimensional electron systems

TL;DR

This study measures the effective mass in dilute, spin-polarized 2D electron systems in AlAs quantum wells, revealing an unexpected suppression of effective mass below the band mass when fully spin-polarized.

Contribution

It demonstrates the novel phenomenon of effective mass suppression below the band mass in fully spin-polarized 2DESs, contrasting with previous observations of mass enhancement.

Findings

Effective mass increases with partial spin polarization.

Effective mass is suppressed below the band mass in full spin polarization.

Results challenge existing theories on electron interactions in 2DESs.

Abstract

We report effective mass (m*) measurements, via analyzing the temperature dependence of the Shubnikov-de Haas oscillations, for dilute, interacting, two-dimensional electron systems (2DESs) occupying a single conduction-band valley in AlAs quantum wells. When the 2DES is partially spin-polarized, m* is larger than its band value, consistent with previous results on various 2DESs. However, as we fully spin polarize the 2DES by subjecting it to strong parallel magnetic fields, m* is unexpectedly suppressed and falls even below the band mass.