Modeling interface disorder effects on the spin transport through an antiferromagnetic insulator
Final Report Abstract
While in electronics information is carried by electric signals and electric currents, in spintronics information is stored and carried by angular momentum or spin. Specifically, insulator spintronics might be of great interest for future energy-efficient logic devices due to the fact that there are no moving charges and therefore no Joule heating which is the biggest source of energy loss in an electronic device. Spin current in magnetically ordered insulators is carried by spin waves which are excitations to the magnetically ordered ground state. Quantized spin waves are called magnons. In this project, we investigated the magnon-carried spin transport and other magnon-related phenomena. One main focus was on interfacial spin transport between antiferromagnetically ordered insulators and metals where spin transport is carried by spin-polarized electrons. These interfaces are highly relevant for generation and detection of spin current in insulators. Namely, we computed the spin current in a trilayer of a metal, the antiferromagnetic insulator NiO and the ferromagnetic insulator yttrium iron garnet. We predict an even-odd effect depending on the number of atomic NiO layers for the sign of the spin current. Furthermore, we investigated the effect of interfacial disorder on the spin current between a metal and an antiferromagnetic insulator and found that disorder leads to a decrease in the spin current specifically for low temperatures. As another magnon-related phenomenon, this project contributed to research on predicting superconductivity in a metal-antiferromagnetic insulator system where the magnons in the antiferromagnet (in contrast to phonons) generate the effective electron-electron coupling. Moreover, this project contributed to computing entanglement between magnons in antiferromagnetic insulators as well as in ferromagnetic layers coupled by dipole-dipole interaction. This entanglement might be a resource in future quantum information processing or quantum communication applications.
Publications
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Superconductivity at metal-antiferromagnetic insulator interfaces. Physical Review B, 100(12).
Fjærbu, Eirik Løhaugen; Rohling, Niklas & Brataas, Arne
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Theory of quantum entanglement and structure of the two-mode squeezed antiferromagnetic magnon vacuum. Physical Review B, 105(5).
Wuhrer, D.; Rohling, N. & Belzig, W.
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Even-odd effect for spin current through a thin antiferromagnetic insulator. Physical Review B, 108(21).
Rohling, Niklas & Troncoso, Roberto E.
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Dipole–dipole-interaction-induced entanglement between two-dimensional ferromagnets. Applied Physics Letters, 125(2).
Wuhrer, D.; Rohling, N. & Belzig, W.
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Influence of disorder at insulator-metal interface on spin transport. Physical Review B, 111(5).
Seyed, Heydari Mahsa; Belzig, Wolfgang & Rohling, Niklas
