Ab initio description of the diluted magnetic semiconductor Ga_1-xMn_xAs: Ferromagnetism, electronic structure, and optical response

Motivated by a study of various experiments describing the electronic and magnetic properties of the diluted magnetic semiconductor Ga_1-xMn_xAs, we investigate its physical response in detail using a combination of first-principles band structure with methods based on dynamical mean field theory to incorporate strong, dynamical correlations, and intrinsic as well as extrinsic disorder in one single theoretical picture. We show how ferromagnetism is driven by double exchange (DE), in agreement with very recent observations, along with a good quantitative description of the details of the electronic structure, as probed by scanning tunneling microscopy and optical conductivity. Our results show how ferromagnetism can be driven by DE even in diluted magnetic semiconductors with small carrier concentration.