RIKEN Center for Emergent Matter Science Emergent Functionality Design Research Unit

Unit Leader: Shun Okumura (Ph.D)

Japanese Page

Research Summary

Our unit theoretically investigates emergent functionalities in quantum materials, such as electrical conductivity and magnetism. We use numerical and analytical calculations to explore the rich functional phenomena in strongly correlated electron systems where various degrees of freedom interact, such as charge, spin, orbital, and sublattice. Specifically, we calculate the electrical and optical conductivity by linear and nonlinear response theory, numerically simulate thermal equilibrium states and non-equilibrium dynamics, and design new materials based on first-principles calculations for spin-charge coupled systems, topological magnetic textures, and topological electronic states.

Main Research Fields

Mathematical & Physical Sciences

Related Research Fields

Engineering
Interdisciplinary Science & Engineering
Physics
Applied Physics
Material engineering

Keywords

Topological materials
Strongly correlated electron systems
Theoretical materials design
Magnetic monopoles
Spintronics

Selected Publications

Papers with an asterisk(*) are based on research conducted outside of RIKEN.

1. Akatsuka, S., Esser, S., Okumura, S., Yambe, R., Yamada, R., Hirschmann, M. M., Aji, S., White, J. S., Gao, S., Onuki, Y., Arima, T., Nakajima, T., and Hirschberger, M.:
"Non-coplanar helimagnetism in the layered van-der-Waals metal DyTe₃"
Nat. Commun. 15, 4291 (2024).
2. *Hirai, Y., Okumura, S., Yoshikawa, N., Oka, T., and Shimano, R.;
"Floquet Weyl states at one-photon resonance: An origin of nonperturbative optical responses in three-dimensional materials"
Phys. Rev. Research 6, L012027 (2024).
3. *Okumura, S., Kravchuk, V. P., and Garst, M.:
"Instability of Magnetic Skyrmion Strings Induced by Longitudinal Spin Currents"
Phys. Rev. Lett. 131, 066702 (2023).
4. *Okumura, S., Hayami, S., Kato, Y., and Motome, Y.:
"Magnetic Hedgehog Lattice in a Centrosymmetric Cubic Metal"
J. Phys. Soc. Jpn. 91, 093702 (2022).
5. *Okumura, S., Morimoto, T., Kato, Y., and Motome, Y.:
"Quadratic optical responses in a chiral magnet"
Phys. Rev. B 104, L180407 (2021).
6. *Morimoto, T., Kitamura, S., and Okumura, S.:
"Electric polarization and nonlinear optical effects in noncentrosymmetric magnets"
Phys. Rev. B 104, 075139 (2021).
7. *Shimizu, K., Okumura, S., Kato, Y., and Motome, Y.:
"Spin Moiré Engineering of Emergent Electromagnetism"
Phys. Rev. B 103, 184421 (2021).
8. *Okumura, S., Hayami, S., Kato, Y., and Motome, Y.:
"Magnetic hedgehog lattices in noncentrosymmetric metals"
Phys. Rev. B 101, 144416 (2020).
9. *Okumura, S., Ishizuka, H., Kato., Y., Ohe, J., and Motome, Y.:
"Spin-current diode with a monoaxial chiral magnet"
Appl. Phys. Lett. 115, 102401 (2019).
10. *Okumura, S., Kato, Y., and Motome, Y.:
"Lock-in of a Chiral Soliton Lattice by Itinerant Electrons"
J. Phys. Soc. Jpn. 87, 033708 (2018).

Lab Members

Principal investigator

Shun Okumura: Unit Leader

Contact Information

313, Fac. of Eng. Bldg. 6, The University of Tokyo,
7-3-1, Hongo, Bunkyo-ku, Tokyo
Email: shun.okumura@riken.jp