Regensburg 2016 – scientific programme

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MA: Fachverband Magnetismus

MA 30: Spin-Torque Phenomena

MA 30.12: Talk

Wednesday, March 9, 2016, 13:00–13:15, H33

Mixed Berry curvatures from first principles — •Jan-Philipp Hanke, Frank Freimuth, Stefan Blügel, and Yuriy Mokrousov — Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, 52425 Jülich, Germany

Both spin-orbit torques (SOT) and Dzyaloshinskii-Moriya interaction (DMI) arise in systems combining broken inversion symmetry and spin-orbit coupling. In a Berry phase theory the two phenomena are intimately related through the mixed Berry curvature which incorporates wave function derivatives with respect to crystal momentum k and magnetization direction m [1]. Performing the differentiation with respect to magnetization direction, however, renders the first-principles evaluation of the mixed Berry curvature a conceptually difficult task. Here, we present a scheme that grants efficient but accurate access to general mixed (and pure) Berry curvatures. Starting from the first-principles electronic structure, we employ higher-dimensional Wannier functions (HDWFs) [2] as minimal basis to treat the aforementioned wave function derivatives on an equal footing. We apply our method to Mn/W(001) where we analyze the mixed Berry curvature throughout ( k, m) phase space. Using the Berry phase expressions, we further compute SOT and DMI in the system and study the anisotropy with respect to magnetization direction.

[1] F. Freimuth et al., J. Phys. Condens. Matter 26, 104202 (2014)

[2] J.-P. Hanke et al., Phys. Rev. B 91, 184413 (2015)