(Ga,Mn)As is a paradigm diluted magnetic semiconductor which shows ferromagnetism induced by doped hole carriers. With a few controversial models emerged from numerous experimental and theoretical studies, the mechanism of the ferromagnetism in (Ga,Mn)As still remains a puzzling enigma. In this Letter, we use soft x-ray angle-resolved photoemission spectroscopy to positively identify the ferromagnetic Mn 3d-derived impurity band in (Ga,Mn)As. The band appears hybridized with the light-hole band of the host GaAs. These findings conclude the picture of the valence band structure of (Ga,Mn)As disputed for more than a decade. The non-dispersive character of the IB and its location in vicinity of the valence-band maximum indicate that the Mn 3d-derived impurity band is formed as a split-off Mn-impurity state predicted by the Anderson impurity model. Responsible for the ferromagnetism in (Ga,Mn)As is the transport of hole carriers in the impurity band.
@article{arxiv.1302.0063,
title = {Unveiling the impurity band inducing ferromagnetism in magnetic semiconductor (Ga,Mn)As},
author = {Masaki Kobayashi and Iriya Muneta and Yukiharu Takeda and Yoshihisa Harada and Atsushi Fujimori and Juraj Krempasky and Thorsten Schmitt and Sinobu Ohya and Masaaki Tanaka and Masaharu Oshima and Vladimir N. Strocov},
journal= {arXiv preprint arXiv:1302.0063},
year = {2014}
}