PGI-1 Talk: Prof. Dr. Shuichi Murakami
Quantum Theory of Materials Seminar
Theory of chiral phonons and their conversions to spin polarizations
Phonons are can have rotational motions in some materials. Such phonons are called chiral phonons [1-4]. For example, in systems with chiral structure such as tellurium, phonon modes possess angular momenta. We study novel phenomena associated with phonon angular momentum by using an analogy to electron spins.
We have theoretically shown that chiral phonons induce spin magnetization in electronic systems [5]. This phenomenon is caused by dynamic modulation of electronics states by chiral phonons, which induces a spin polarization. Furthermore, in ferromagnets and antiferromagnets, we found that chiral phonons induce changes in magnon excitations. This shows that chiral phonons can serve as an effective magnetic field for electrons and magnons [5,6], and this scenario can be a microscopic mechanism for spin-rotation coupling. In addition, we show that in inversion-asymmetric systems, chiral phonons can induce a current as well [7]. The induced current is nonzero in metals but is zero in insulators.
[1] L. Zhang, Q. Niu Phys. Rev. Lett. 112, 085503 (2014).
[2] T. Zhang, S. Murakami, Phys. Rev. Research 4, L012024 (2022).
[3] K. Ishito et al., Nat. Phys. 19, 35 (2022).[4] M. Hamada, E. Minamitani, M. Hirayama, S. Murakami, Phys. Rev. Lett. 121, 175301 (2018).
[5] M. Hamada, S. Murakami, Phys. Rev. Research 2, 023275 (2020).
[6] D. Yao, S. Murakami, Phys. Rev. B 105, 184412 (2022)
[7] D. Yao, S. Murakami, J. Phys. Soc. Jpn. 93, 034708 (2024).
Contact
Prof. Dr. Yuriy Mokrousov
Phone: +49 2461 61- 4434
Email: y.mokrousov@fz-juelich.de
Prof. Dr. Shuichi Murakami
Department of Physics, Institute of Science Tokyo
Department of Physics, Tokyo Institute of Technology
WPI-SKCM2, Hiroshima University
Email: murakami@stat.phys.titech.ac.jp