Seminar – Takeo Kato

Takeo Kato (Institute for Solid State Physics, University of Tokyo) will give a seminar on June 5th 2025 at the TRT Thales auditorium.

Title:
Spin-Chiral Phonon Conversion in Nonmagnetic Metal-Chiral Insulator Junctions

Abstract:
Recently, phonon-spin interconversion phenomena have attracted considerable attention as manifestations related to chirality-induced spin selectivity (CISS). Despite numerous investigations [1], the microscopic mechanism governing the interconversion between chiral phonons and electron spins remains unresolved. In this study [2], we develop a theoretical framework for this interconversion by considering the gyromagnetic effect. We analyze a junction system composed of a nonmagnetic metal and a chiral insulator and derive a spin-microscopic rotation coupling at the interface. We demonstrate that a non-equilibrium distribution of chiral phonon modes, induced by a temperature gradient, can generate a spin current across the junction, in consistent with the recent experiment [3]. We also mention extension of this theoretical framework to CISS effect in DNA [4].

References :
[1] Y. Togawa et al., J. Phys. Soc. Jpn. 92 (2023) 081006.
[2] T. Funato, M. Matsuo, and T. Kato, Phys. Rev. Lett. 132, 236201 (2024).
[3] K. Ohe, et al., Phys. Rev. Lett. 132, 056302 (2024).
[4] R. Sano and T. Kato, preprint (arXiv:2404.19000).