High-magnetic-field Zeeman spectroscopy of the 0.84-eV Cr-related emission and absorption line in GaAs(Cr): Experiment and theory

The results of a series of high-magnetic-field (up to 22 T) Zeeman-spectroscopy measurements are reported on the Cr-related 0.84-eV luminescence line in GaAs. The observed Zeeman splitting and oscillator strengths can be satisfactorily explained in terms of a model in which both the excited and ground state have $C_{3v}$ symmetry and a twofold-orbital and fivefold-spin ($S=2\mathrm{}$) nature. In addition the model provides an excellent fit to the oscillator strengths and energies of the fine structure observed in the no-phonon line seen at zero magnetic field in both absorption and luminescence. Our result conclusively demonstrates that a recently proposed model based on a ground-state effective Hamiltonian containing terms of only cubic symmetry is incorrect.