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Spin-derived electric polarization and chirality density inherent in localized electron orbitals

Date : Monday, March 27th, 2023 4:00 pm - 5:00 pm Place : Online (Zoom) Lecturer : Shintaro HOSHINO Affiliation : Saitama University Committee Chair : Hirokazu Tsunetsugu (ex. 63597)
e-mail: tsune@issp.u-tokyo.ac.jp

In solid state physics, any phase transition is commonly observed as a change in the microscopic distribution of charge, spin, or current. However, there is an exotic order parameter inherent in the localized electron orbitals that cannot be primarily captured by these three fundamental quantities.
This order parameter is described as the electric toroidal multipoles connecting different total angular momenta under the spin-orbit coupling. The corresponding microscopic physical quantity is the spin current tensor on an atomic scale, which induces spin-derived electric polarization aligned circularly and the chirality density derived from the Dirac equation [1].
We also derive the equation of continuity for chirality density and discuss its relation to chiral anomaly and optical chirality. These findings link microscopic spin currents and chirality in the Dirac theory to the concept of multipoles and provide a new perspective for quantum states of matter.

This work has been done in collaboration with H. Ikeda and M.-T. Suzuki.

[1] S. Hoshino, M.-T. Suzuki, H. Ikeda, arXiv:2210.02148 (2022).


(Published on: Monday March 20th, 2023)