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

摘要

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