DATE2022.01.14 #Press Releases

Unified electromagnetic response of electrons in solids

Disclaimer: machine translated by DeepL which may contain errors.

-Quantization of large antimagnetism and electrical conduction in molecular solids

RIKEN

Graduate School of Science, The University of Tokyo

Toho University

Summary

A joint research group led by Shigeki Fujiyama, Member (at the time of the research) and Reizo Kato, Senior Staff (currently Research Policy Director at RIKEN) at the Kato Laboratory for Molecular Physics, Central Administration Bureau, RIKEN, Hideaki Maebashi, Senior Staff at the Graduate School of Science, The University of Tokyo, and Professor Naoya Tajima at the Faculty of Science, Toho University, has discovered a scaling law (proportionality relation) between the magnetic susceptibility and electrical conductivity of a material called "Dirac fermions". The research group has discovered a scaling law (proportionality relation) between the magnetic susceptibility and electrical conductivity of a material called "Dirac electron system," and found that the unification of this electromagnetic response corresponds to the "symmetry of time and space" in the special theory of relativity.

The research results are expected to provide a basis for understanding the electromagnetic response of candidate materials for next-generation devices, such as graphene and topological insulators.

In this study, the research group identified the molecular solid α-(BETS) _2I3 as a two-dimensional Dirac fermions with a small energy gap (energy range where no electronic state exists) from experiments and band calculations, and measured its magnetic susceptibility and electrical conductivity. We observed a large orbital antimagnetic susceptibility that occurs only in the direction perpendicular to the two-dimensional conduction plane, and derived a scaling law with the quantized electrical conductivity. This strong relationship between magnetism and electrical conduction is derived from the equivalence of the dispersion relation of zero-gap Dirac electrons and that of light, which corresponds to the symmetry in time and space derived by the special theory of relativity.

This study was published online (January 12) prior to its publication in the scientific journal Physical Review Letters (January 14).

Figure: Scaling of electrical conductivity and antimagnetic susceptibility (proportional relationship, solid red line is theoretical calculation)

Professor Masao Ogata and Project Researcher Hideaki Maebashi of the Department of Physics participated in this research.

For more details, please visit the RIKEN website.