Large-Scale Monte Carlo Study of a Realistic Lattice Model for Ga_(1-x)Mn_xAs

TL;DR

This study uses large-scale Monte Carlo simulations on a realistic lattice model to analyze the magnetic and electronic properties of Mn-doped GaAs, achieving results consistent with experimental data and providing insights into the nature of charge carriers.

Contribution

It introduces a comprehensive real-space Hamiltonian model for GaMnAs and performs large-scale simulations that incorporate spin-orbit interaction and disorder, aligning theoretical predictions with experiments.

Findings

Monte Carlo Curie temperature matches experimental values for annealed samples.

Magnetization curves are consistent with experimental observations.

System behaves more like a hole-fluid than a localized carrier regime.

Abstract

The properties of Mn-doped GaAs are studied at several doping levels and hole compensations, using a real-space Hamiltonian on an fcc lattice that reproduces the valence bands of undoped GaAs. Large-scale Monte Carlo (MC) simulations on a Cray XT3 supercomputer, using up to a thousand nodes, were needed to make this effort possible. Our analysis considers both the spin-orbit interaction and the random distribution of the Mn ions. The hopping amplitudes are functions of the GaAs Luttinger parameters. At the coupling J~1.2eV deduced from photoemission experiments, the MC Curie temperature and the shape of the magnetization curves are in agreement with experimental results for annealed samples. Although there are sizable differences with mean-field predictions, the system is found to be closer to a hole-fluid regime than to localized carriers.