  After two decades from the discovery of ferromagnetism in Mn-doped GaAs, its
origin is still debated, and many doubts are related to the electronic
structure. Here we report an experimental and theoretical study of the valence
electron spectrum of Mn-doped GaAs. The experimental data are obtained through
the differences between off- and on-resonance photo-emission data. The
theoretical spectrum is calculated by means of a combination of
density-functional theory in the local density approximation and dynamical
mean-field theory (LDA+DMFT), using exact diagonalisation as impurity solver.
Theory is found to accurately reproduce measured data, and illustrates the
importance of correlation effects. Our results demonstrate that the Mn states
extend over a broad range of energy, including the top of the valence band, and
that no impurity band splits off from the valence band edge, while the induced
holes seem located primarily around the Mn impurity.
