The non-metal-to-metal and Vice-Versa transitions in a GaMnAs layer
Résumé
A self-consistent calculation of the density of states and the spectral density function is performed in a two-dimensional spin-polarized hole system based on a multiple-scattering approximation. Using parameters corresponding to GaMnAs thin layers, a wide range of Mn concentrations and hole densities have been explored to understand the nature, localized or extended, of the spin-polarized holes at the Fermi level for several values of the average magnetization of the Mn system. If the impurity concentration is below a certain threshold, the increase of the magnetization does not lead to a significant change in the localized character of the spin-polarized states. Above this threshold, we reach conditions allowing the occurrence of spin-polarized extended states at the Fermi level-more properly extended states in a very dirty metal-which are very sensitive to the average magnetization. The occurrence of a metal-to-non-metal transition has been surveyed around an optimum combination of the Mn concentration and the free carriers density.