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arXiv · 1606.02047

Fermi level position, Coulomb gap, and Dresselhaus splitting in (Ga,Mn)As

S. Souma·L. Chen·R. Oszwaldowski·T. Sato·F. Matsukura·T. Dietl·H. Ohno·T. Takahashi
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Abstract

Carrier-induced nature of ferromagnetism in a ferromagnetic semiconductor, (Ga,Mn)As, offers a great opportunity to observe novel spin-related phenomena as well as to demonstrate new functionalities of spintronic devices. Here, we report on low-temperature angle-resolved photoemission studies of the valence band in this model compound. By a direct determination of the distance of the split-off band to the Fermi energy EF, we conclude that EF is located within the heavy/light hole band. However, the bands are strongly perturbed by disorder and disorder-induced carrier correlations that lead to the Coulomb gap at EF, which we resolve experimentally in a series of samples, and show that its depth and width enlarge when the Curie temperature decreases. Furthermore, we have detected surprising linear magnetic dichroism in photoemission spectra of the split-off band. By a quantitative theoretical analysis we demonstrate that it arises from the Dresselhaus-type spin-orbit term in zinc-blende crystals. The spectroscopic access to the magnitude of such asymmetric part of spin-orbit coupling is worthwhile, as they account for spin-orbit torque in spintronic devices of ferromagnets without inversion symmetry.

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S. Souma, L. Chen, R. Oszwaldowski, T. Sato, F. Matsukura, T. Dietl, H. Ohno, T. Takahashi. 2016-06-07. Fermi level position, Coulomb gap, and Dresselhaus splitting in (Ga,Mn)As. https://doi.org/10.1038/srep27266

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