Unified picture for diluted magnetic semiconductors

Abstract

For already a decade the field of diluted magnetic semiconductors (DMS) is one of the hottest. In spite of the great success of material specific Density Functional Theory (DFT) to provide accurately critical Curie temperatures ($T_{C}$) in various III-V based materials, the ultimate search for a unifying model/theory was still an open issue. Many crucial questions were still without answer, as for example: Why, after one decade, does GaMnAs still exhibit the highest $T_{C}$? Is there any intrinsic limitations or any hope to reach room temperature? How to explain in a unique theory the proximity of GaMnAs to the metal-insulator transition, and the change from RKKY couplings in II-VI materials to the double exchange regime in GaMnN? The aim of the present work is to provide this missing theory. We will show that the key parameter is the position of the Mn level acceptor and that GaMnAs has the highest $T_{C}$ among III-V DMS. Our theory (i) provides an overall understanding, (ii) is quantitatively consistent with existing DFT based studies, (iii) able to explain both transport and magnetic properties in a broad variety of DMS and (iv) reproduces the $T_{C}$ obtained from first principle studies for many materials including both GaMnN and GaMnAs. The model also reproduces accurately recent experimental data of the optical conductivity of GaMnAs and predicts those of other materials.