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

We analyzed microscopically the valence and impurity band models of ferromagnetic (Ga,Mn)As. We found that the tight-binding Anderson approach with conventional parametrization and the full potential local−density approximation+U calculations give a very similar band structure whose 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. Institute of Physics has been responsible for the work concept and theory (purely theoretical work).

Partial As p-orbital (a) and Mn d-orbital (b) DOSs at EF in the depicted TBA models. The remaining contribution to the total DOS is primarily due to Ga and Mn p orbitals with their relative weights given nearly precisely by the Ga/Mn ratio. (c) The p−d coupling strength in the TBA models compared with the LDA (triangles) and LDA+U (circles) results. (d)–(f) Total DOSs showing the merging of the IB into the VB in the depicted tight-binding models.

¹Institute of Physics ASCR, v.v.i., Na Slovance 2, 182 21 Praha 8, Czech Republic
²School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, United Kingdom
³Institute of Physics ASCR, v.v.i., Cukrovarnická 10, 162 53 Praha 6, Czech Republic
⁴Department of Physics, Texas A&M University, College Station, Texas 77843-4242, USA