Abstract
We study spin-orbit torques and transport properties of Dirac electrons on the surface of ferromagnetic topological insulators. A focus is on the effects of deviation from the ideal Dirac model with linear dispersion, which takes an additional scalar form, quadratic in wave vector, and breaks particle-hole symmetry. This term removes some peculiar features of the linear Dirac model, and, combined with in-plane magnetization, gives rise to in-plane anisotropies. We study in detail the chemical potential dependence of longitudinal/transverse conductivities and reactive/dissipative spin-orbit torques, including the out-of-plane spin polarization. It is found that the in-plane anisotropy is generally stronger for -type carriers than -type carriers (for positive curvature of the quadratic term). It is also found that the in-plane anisotropy of the dissipative spin-orbit torque changes sign across the Dirac point. Because of the similarity of the model, we also study the magnetic Rashba model focusing on its Dirac-like parameter region. In this model, with an in-plane magnetization, a curious discontinuity is found at the Dirac point in the current-induced out-of-plane spin polarization.
4 More- Received 2 December 2020
- Accepted 29 March 2021
DOI:https://doi.org/10.1103/PhysRevB.103.144416
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