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.

中文翻译：

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费米能级位置，库仑间隙和Dresselhaus在（Ga，Mn）As中分裂。

铁磁半导体（Ga，Mn）As中铁磁的载流子诱导性质为观察新型自旋相关现象以及演示自旋电子器件的新功能提供了巨大的机会。在这里，我们报告在此模型化合物的价带的低温角度分辨的光发射研究。通过直接确定分离带到费米能量EF的距离，我们得出结论，EF位于重/轻空穴带内。然而，这些谱带被无序和无序诱导的载流子相关性所强烈干扰，这导致了EF处的库仑缺口，我们在一系列样品中通过实验解析了该谱带，并表明当居里温度降低时，其深度和宽度会增大。此外，我们已经在分离带的光发射光谱中检测到令人惊讶的线性磁二向色性。通过定量理论分析，我们证明了它来自闪锌矿晶体中的Dresselhaus型自旋轨道项。在光谱上接近自旋轨道耦合的这种不对称部分的大小是值得的，因为它们解释了铁磁体自旋电子器件中的自旋轨道转矩而没有反对称性。