Spin polarization in modulation-doped GaAs quantum wires

TL;DR

This paper investigates how spin polarization in GaAs quantum wires varies with electron density, considering realistic impurity potentials, and finds that lower densities induce significant spin polarization and electron trapping effects.

Contribution

It provides a detailed analysis of spin polarization behavior in quantum wires with realistic impurity potentials using density functional theory, highlighting density-dependent phenomena.

Findings

High electron density results in negligible spin polarization.

Decreasing density leads to rapid spin polarization and electron trapping.

Results align qualitatively with experimental observations.

Abstract

We study spin polarization in a split-gate quantum wire focussing on the effect of a realistic smooth potential due to remote donors. Electron interaction and spin effects are included within the density functional theory in the local spin density approximation. We find that depending on the electron density, the spin polarization exhibits qualitatively different features. For the case of relatively high electron density, when the Fermi energy $E_{F}$ exceeds a characteristic strength of a long-range impurity potential $V_{donors}$, the density spin polarization inside the wire is practically negligible and the wire conductance is spin-degenerate. When the density is decreased such that $E_{F}$ approaches $V_{donors}$, the electron density and conductance quickly become spin polarized. With further decrease of the density the electrons are trapped inside the lakes (droplets) formed by the impurity potential and the wire conductance approaches the pinch-off regime. We discuss the limitations of DFT-LSDA in this regime and compare the obtained results with available experimental data.