Kato Group

Associate Professor

KATO,Takeo

Research Associate

SAKANO,Rui

We are theoretically studying quantum transport in nano-scale devices using analytic and numerical approaches. This research field is called ‘mesoscopic physics’, which has been studied for long time by focusing on quantum mechanical nature of electrons. Recently, mesoscopic physics based on new viewpoints, for instance, nonequilibrium many-body phenomena, shot noise, high-speed drive phenomena, and spintronics, has been studied. We aim to elucidate these phenomena, by exploiting nonequilibrium statistical mechanics, fundamental theory of quantum mechanics, and many-body physics. Examples of our research activities are adiabatic pumping in nanoscale devices, spin transport at an interface between a ferromagnet insulator and a metal, many-body effect in thermal transport of phonons, and nonequilibruim transport properties of the Kondo quantum dots. In addition, we are working on various research subjects related to many-body effects and nonequilibrium phenomena. Examples of these researches are structural phase transition in solid oxygen and higher harmonics generation in solids. We are also collaborating with experimental groups in ISSP.

Main panel: Electronic charge carried by adiabatic pumping induced by the time-dependent lead temperatures, *T*_{L}(t) and *T*_{R}(t), per a cycle. Inset: A schematic of the system. Here, *U* is the Coulomb interaction, Γ_{L }= Γ_{R }= Γ/2 is the lead-dot coupling, ε_{d} is the energy level of the quantum dot, and *u* = *U*/Γ is a dimensionless parameter of the Coulomb interaction.

Upper two figures: Schematics for two mechanisms of spin-current generation (spin Seebeck effect and spin pumping). Lower panel: Temperature dependence of nonequilibrium spin-current noises due to the spin Seebeck effect, the spin pumping, and a thermal noise.

- Quantum transport phenomena in mesoscopic systems
- Properties of interacting electron systems
- Non-equilibrium statistical mechanics and spintronics

1.

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Surface plasmon polaritons in thin-film Weyl semimetals: T. Tamaya, T. Kato, K. Tsuchikawa, S. Konabe and S. Kawabata, J. Phys.: Condens. Matter **31** (2019) 305001(1-10).

2.

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Bell-state correlations of quasiparticle pairs in the nonlinear current of a local Fermi liquid: R. Sakano, A. Oguri, Y. Nishikawa and E. Abe, Phys. Rev. B **99** (2019) 155106(1-7).

3.

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Microscopic theory of spin transport at the interface between a superconductor and a ferromagnetic insulator: T. Kato, Y. Ohnuma, M. Matsuo, J. Rech, T. Jonckheere and T. Martin, Phys. Rev. B **99** (2019) 144411(1-8).

4.

Transport Processes and Quantum Critical Phenomena in Heat Transport via a Two-State System: T. Yamamoto, Graduate School of Science, The University of Tokyo (2019).

5.

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mVMC—Open-source software for many-variable variational Monte Carlo method: T. Misawa, S. Morita, K. Yoshimi, M. Kawamura, Y. Motoyama, K. Ido, T. Ohgoe, M. Imada and T. Kato, Comput. Phys. Commun. **235** (2019) 447-462.