Effective mass suppression upon complete spin-polarization in an isotropic two-dimensional electron system

TL;DR

This study investigates how the effective mass of electrons in a two-dimensional AlAs quantum well changes with spin polarization, revealing a suppression to near or below the band mass upon full spin polarization, highlighting a fundamental property of interacting 2D electrons.

Contribution

It demonstrates the effective mass suppression in an isotropic 2D electron system upon full spin polarization, extending previous findings to a new quantum well configuration.

Findings

Effective mass decreases to near or below band mass at full spin polarization.

Mass enhancement occurs at partial spin polarization and lower densities.

Results support the intrinsic nature of mass suppression in 2D electron systems.

Abstract

We measure the effective mass (m*) of interacting two-dimensional electrons confined to a 4.5 nm-wide AlAs quantum well. The electrons in this well occupy a single out-of-plane conduction band valley with an isotropic in-plane Fermi contour. When the electrons are partially spin polarized, m* is larger than its band value and increases as the density is reduced. However, as the system is driven to full spin-polarization via the application of a strong parallel magnetic field, m* is suppressed down to values near or even below the band mass. Our results are consistent with the previously reported measurements on wide AlAs quantum wells where the electrons occupy an in-plane valley with an anisotropic Fermi contour and effective mass, and suggest that the effective mass suppression upon complete spin polarization is a genuine property of interacting two-dimensional electrons.