Theory of charge and spin pumping in atomic-scale spiral magnets
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| Main Authors: | , , , |
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| Format: | Preprint |
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2022
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| _version_ | 1866916111408168960 |
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| author | Kurebayashi, Daichi Liu, Yizhou Masell, Jan Nagaosa, Naoto |
| author_facet | Kurebayashi, Daichi Liu, Yizhou Masell, Jan Nagaosa, Naoto |
| contents | An Archimedean screw is a classical pump that exploits the equivalence of rotation and translation in helices. Similarly, a spin spiral texture can pump charge and spin by rotating at a frequency $ω$. In the present paper, we study these pumping phenomena within a microscopic quantum model by both perturbation theory and numerical simulations. Inside the spiral region, the spin polarization and charge current are linear in $ω$ whereas the spin current is $ω^2$ for small $ω$. We find that the charge current is related to the mixed momentum-phason Berry phase, which can be viewed as a novel approximate realization of a Thouless pump. It is nearly quantized in spirals with short pitch $λ$ but decays with $λ^{-1}$ for longer pitches, unlike true Thouless pumps or Archimedian screws. Moreover, we study the onset of non-adiabaticity (large $ω$), the impact of attached non-magnetic or magnetic contacts, and the real-time evolution of the transport observables. Finally, we analyze the effects of disorders which, surprisingly, might enhance the spin current but suppress the charge current. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2201_05446 |
| institution | arXiv |
| publishDate | 2022 |
| record_format | arxiv |
| spellingShingle | Theory of charge and spin pumping in atomic-scale spiral magnets Kurebayashi, Daichi Liu, Yizhou Masell, Jan Nagaosa, Naoto Mesoscale and Nanoscale Physics An Archimedean screw is a classical pump that exploits the equivalence of rotation and translation in helices. Similarly, a spin spiral texture can pump charge and spin by rotating at a frequency $ω$. In the present paper, we study these pumping phenomena within a microscopic quantum model by both perturbation theory and numerical simulations. Inside the spiral region, the spin polarization and charge current are linear in $ω$ whereas the spin current is $ω^2$ for small $ω$. We find that the charge current is related to the mixed momentum-phason Berry phase, which can be viewed as a novel approximate realization of a Thouless pump. It is nearly quantized in spirals with short pitch $λ$ but decays with $λ^{-1}$ for longer pitches, unlike true Thouless pumps or Archimedian screws. Moreover, we study the onset of non-adiabaticity (large $ω$), the impact of attached non-magnetic or magnetic contacts, and the real-time evolution of the transport observables. Finally, we analyze the effects of disorders which, surprisingly, might enhance the spin current but suppress the charge current. |
| title | Theory of charge and spin pumping in atomic-scale spiral magnets |
| topic | Mesoscale and Nanoscale Physics |
| url | https://arxiv.org/abs/2201.05446 |