I am working on the following subjects:
- Interconversion between spin and mechanical angular momentum
- Quantum transport of spin and heat at magnetic interfaces
- Spin transport in non-uniform materials
Interconversion between spin and mechanical angular momentum
We developed a theory of interconversion between electron spins and mechanical angular momentum of materials. In a material with mechanical angular momentum, electron spins couple to vorticity. As a result, we can control spin dynamics without magnetism and strong spin-orbit coupling. The spin-vorticity coupling allows us to utilize materials, which have not been considered as a suitable material for a spin source, such as Cu and Ga because of their small spin-orbit coupling.
Our predictions on angular momentum conversions using spin-vorticity coupling [PRL2011, PRB2013(R), PRB2017(R)] are experimentally demonstrated in liquid metals [Nature Physics 2016, Nature Comm 2020 , PRApplied2020], elastic materials [PRL2017, PRL 2020, Nature Comm 2019], and rigid bodies [SciRept 2017].
Quantum transport of spin and heat at magnetic interfaces
We have been developing a microscopic theory of spin an heat at magnetic interfaces. Recently, we formulate spin current noise at the interface of normal metal/ferromagnet systems [PRL2018]. We would like to harmonize two established research fields; mesoscopic physics and spintronics.
We also study valley-dependent spin transport theoretically in monolayer transition-metal dichalcogenides in which a variety of spin and valley physics are expected because of spin-valley coupling. The results indicate that spin excitations with spin-valley coupling lead to both valley and spin transport, which is promising for future low-consumption nanodevice applications [PRL2020].
Spin transport in non-uniform materials
Recently, we found a nontrivial spin transport in a naturally oxidized Cu, where the conductivity of electrons is non-uniform. In such a system, the vorticity of the charge current is created so that a spin current is generated via the spin-vorticity coupling. Interestingly, in this system, the reciprocal process, spin-to-charge conversion process, is strongly suppressed [PRL2019].