Microscopic analysis of the valence band and impurity band theories of (Ga,Mn)As

TL;DR

This study microscopically compares valence and impurity band models of ferromagnetic (Ga,Mn)As, finding that the valence band model aligns with detailed calculations, while impurity band models are incompatible with the spectral data.

Contribution

It demonstrates that the valence band model is consistent with microscopic spectral calculations, challenging the impurity band model in ferromagnetic (Ga,Mn)As.

Findings

Valence band states are exchange-split and hybridized with host orbitals.

Impurity band models with detached bands are incompatible with microscopic spectra.

Detached impurity bands do not persist across doping levels in (Ga,Mn)As.

Abstract

We analyze microscopically the valence and impurity band models of ferromagnetic (Ga,Mn)As. We find that the tight-binding Anderson approach with conventional parameterization and the full potential LDA+U calculations give a very similar picture of states near the Fermi energy which reside in an exchange-split sp-d hybridized valence band with dominant orbital character of the host semiconductor; this microscopic spectral character is consistent with the physical premise of the k.p kinetic-exchange model. On the other hand, the various models with a band structure comprising an impurity band detached from the valence band assume mutually incompatible microscopic spectral character. By adapting the tight-binding Anderson calculations individually to each of the impurity band pictures in the single Mn impurity limit and then by exploring the entire doping range we find that a detached impurity band does not persist in any of these models in ferromagnetic (Ga,Mn)As.