Scattering calculations for Spin- and Orbitronics
Max Rang is a PhD student in the Department of Computational Materials Science. Promotor is prof.dr. P.J. Kelly from the Faculty of Science & Technology.
The link between Maxwell’s equations and contemporary electronics motivates the study of electron spin in addition to its electrical charge, so that we may potentially improve on the efficiency and engineering possibilities in designing electronic (or rather, spintronic) devices. The spin and orbital Hall effects are phenomena that are indispensable in spintronics and the newly emerging orbitronics fields. These effects are examples of charge-to-spin conversion, that allow for exerting torques on magnetic domains, i.e. bits in a computer system.
This thesis describes quantum mechanical scattering calculations for material properties in spin- and orbitronics. The calculations were done with the Twente Quantum Transport (TQT) code which solves the Landauer-Büttiker problem using wave-function matching with a basis of tight-binding muffin-tin orbitals (TB-LMTO). The specific material properties under study vary by chapter, but generally they are concerned with the length scale and amplitude of spin andorbital currents, possibly generated by the spin and orbital Hall effects.
We find an intriguing difference between the long length scale of orbital Hall currents that are extracted from experiments on the one hand, and computational predictions (the research in this thesis) on the other. One of the main conclusions of the thesis is thus that our understanding of orbital currents is incomplete and the modeling of experiments needs to be improved. On the other hand, the fundamental understanding of the computations themselves is also lacking, since there are small but significant differences between different theoretical predictions. The precise reason for those discrepancies is uncertain.
Spintronics and its new cousin orbitronics are fundamentally interesting fields of physics that have significant technological potential. To push the field of orbitronics out of its infancy, more fundamental understanding is necessary. The research in this thesis is an attempt at generating such knowledge, by developing a computer code (i.e. TQT) that provides a unique perspective and producing novel results, especially compared to other theoretical studies.
