Cryogenic Research Center, The University of Tokyo

Graduate School of Science, The University of Tokyo

Institute for Materials Research, Tohoku University

Japan Science and Technology Agency

Summary of Announcement

A research group led by Professor Ryo Shimano at the Cryogenic Research Center of the University of Tokyo, Assistant Professor Naotaka Yoshikawa and graduate student Kazuma Ogawa at the Graduate School of Science of the University of Tokyo, Professor Atsushi Tsukazaki and Associate Professor Kohei Fujiwara at the Institute for Materials Research, Tohoku University, under the JST Strategic Basic Research Program for the Promotion of Creative Research, has successfully demonstrated that the chirality and magnetization of electrons in a magnetic Weyl semiconductor, a type of topological material, can be reversed by light. The research group has succeeded in inverting the chirality and magnetization of electrons in magnetic Weyl semimetals, a type of topological material, by means of light.

Electrons in Weil semimetals behave as if they were Weil particles, which are particles with zero mass, and have a degree of freedom called chirality, which is characterized by right-handed and left-handed curvature. In particular, electrons in Weil semimetals, which exhibit magnetism, sense the pseudo-magnetic field generated inside even without an external magnetic field, and exhibit a huge anomalous Hall effect. Since the current produced by this anomalous Hall effect is a current without energy dissipation, it is expected to be used in various applications, such as next-generation quantum devices with low power consumption.

The light-induced magnetization/chirality reversal discovered in this study also inverts the sign of the anomalous Hall effect. This is a new method to control the properties of Weil semimetals using light, since it is possible to control the magnetization and chirality of ferromagnetic Weil semimetals using only light, without the need to apply an external magnetic field such as a magnet to invert the magnetization.

The research results were published online in the British online scientific journal Communications Physics on December 20, 2022 at 10:00 a.m. (UK time).

Figure: Schematic of the chirality inversion of Weil particles by light demonstrated in this study. By irradiating the ferromagnetic Weyl semimetal _Co3Sn2S2 with Kagome lattice with circularly polarized light, the ferromagnetic magnetization and chirality (right-handed: pink, left-handed: green) of the Weyl particles were successfully reversed repeatedly and freely.

For more information, please visit the website of the Cryogenic Research Center , The University of Tokyo.