Title: Theory of CISS Effect in Solid State Physics  

Speaker: Prof. Takeo Kato (ISSP, University of Tokyo)

Time: 10:00 am, Dec.12(Friday),2025

Place:Room M830,IOP-CAS(中国科学院物理研究所M830)  

Abstract
Chirality-induced spin selectivity (CISS), a spin-dependent electronic transportphenomenon arising from the chirality of matter, has been attracting considerableattentlon,Despite extensive theoretical and expermental studies, however.itsmicroscopic mechanism remains unresolved. In this talk, I focus on the magneticrotational efect 1, an angular-momentum conversion phenomenon between electronspins and rigid-body rotations,and introduce a theory of CISS based on theinterconversion between chiral phonons and electron spins 23. In this frameworkwe identify the "microscopic rotations" induced by chiral phonons and derive a spin-microrotation coupling at the interface.Importantly, this coupling requires no spin-.orbit interaction and is therefore expected to describe the CISS effect particularly welin systems composed of light elements.
I will present the chiral-phonon-spin conversion theory for two distinct systemsFirst, we consider a iunction composed of a normal metal (N) and a chiral insulator(CI).Treating the interfacial spin--phonon coupling arising from the magneticrotational effect perturbatively, we analyze the interfacial spin current injected intothe paramagnetic metal under a temperature bias 1]. In this system, a spin current isgenerated at the NM/CI interface due to a nonequilibrium distribution among chira!phonon modes induced by the temperature gradient. Our theoretical results show goodagreement with recent experiments employing a-quartz 3. Second.we examinehopping conduction in DNA, which possesses a helical structure 2.We demonstratethat electron transport driven by an applied voltage leads to spin accumulation nearthe interface, and we compare our results with available experimental data.

References:
[1]. T. Funato, M. Matsuo, and T. Kato, Phys. Rev. Lett. 132.236201 (2024).
[2]. R. Sano and T. Kato, arXiy:2404.19000.
[3]. K. Ohe et al., Phys.Rev.Lett. 132,056302(2024).