Disorder, spin-orbit, and interaction effects in dilute Ga1−xMnxAs

Fiete, Gregory A. ; Zaránd, Gergely ; Damle, Kedar ; Moca, C. Pascu (2005) Disorder, spin-orbit, and interaction effects in dilute Ga1−xMnxAs Physical Review B: Condensed Matter and Materials Physics, 72 (4). Article ID 045212. ISSN 2469-9950

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Official URL: http://journals.aps.org/prb/abstract/10.1103/PhysR...

Related URL: http://dx.doi.org/10.1103/PhysRevB.72.045212


We derive an effective Hamiltonian for Ga1−xMnxAs in the dilute limit, where Ga1−xMnxAs can be described in terms of spin F=3∕2 holes hopping between the Mn sites and coupled to the local Mn spins. We determine the parameters of our model from microscopic calculations using both a variational method and an exact diagonalization within the so-called spherical approximation. Our approach treats the extremely large Coulomb interaction in a nonperturbative way and captures the effects of strong spin-orbit coupling and Mn positional disorder. We study the effective Hamiltonian in a mean-field and variational calculation, including the effects of interactions between the holes at both zero and finite temperature. We study the resulting magnetic properties, such as the magnetization and spin-disorder manifest in the generically noncollinear magnetic state. We find a well-formed impurity band fairly well separated from the valence band up to xactive≲0.015 for which finite-size scaling studies of the participation ratios indicate a localization transition, even in the presence of strong on-site interactions, where xactive<xnom is the fraction of magnetically active Mn. We study the localization transition as a function of hole concentration, Mn positional disorder, and interaction strength between the holes.

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ID Code:103883
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