Strong Correlation Physics Research Group

Principal Investigator
Outline
Members
Publications
Articles

Principal Investigator

PI Name

Yoshinori Tokura

Degree

D.Eng.

Title

Group Director

Brief Resume

1981	D. Eng., University of Tokyo
1986	Associate Professor, University of Tokyo
1994	Professor, Department of Physics, University of Tokyo
1995	Professor, Department of Applied Physics, University of Tokyo
2001	Director, Correlated Electron Research Center, AIST
2007	Group Director, Cross-Correlated Materials Research Group, RIKEN
2008	AIST Fellow, National Institute of Advanced Industrial Science and Technology (-present)
2010	Director, Emergent Materials Department, RIKEN
2010	Group Director, Correlated Electron Research Group, RIKEN
2013	Director, RIKEN Center for Emergent Matter Science (CEMS)
2013	Group Director, Strong Correlation Physics Research Group, Strong Correlation Physics Division, RIKEN CEMS (-present)
2014	Team Leader, Strong Correlation Quantum Transport Research Team, Strong Correlation Physics Division, RIKEN CEMS (-present)
2017	Distinguished University Professor, University of Tokyo (-present)
2019	Special University Professor, University of Tokyo
2024	Special Advisor to the President, RIKEN (-present)

Outline

Our group investigates a variety of emergent phenomena in strongly correlated electron systems, which cannot be understood within the framework of conventional semiconductor/metal physics, to construct a new scheme of science and technology. In particular, we focus on transport, dielectric and optical properties in non-trivial spin/orbital structures, aiming at clarifying the correlation between the response and the spin/orbital state. In addition, we investigate electron systems with strong relativistic spin-orbit interaction, unraveling its impact on transport phenomena and other electronic properties. Target materials include high-temperature superconductors, colossal magnetoresistance systems, multiferroics, topological insulators, and skyrmion materials.

Research Fields

Physics, Engineering, Materials Science

Keywords

Strongly correlated electron system
Topological insulators
Spin-orbit interaction
Berry phase physics
Multiferroics
Skyrmion

Results

Topological spin textures and emergent electromagnetic functions

Nanometric spin texture called “skyrmion”. The skyrmion is the idea coined by Tony Skyrme, a nuclear physicist, to describe a state of nucleon as the topological soliton, It has recently been demonstrated that such a kind of topological particle should exist widely in ubiquitous magnetic solids. The arrows in the figure represent the directions of the spin (electron’s magnetic moment); the spins direct up at the peripheral, swirl in going to the inside, and direct down at the core. This topology cannot be reached via continuous deformation from the conventional spin orders, meaning that the skyrmion can be viewed by a topologically protected particle. The skyrmion can carry a fictitious (emergent) magnetic field working on moving conduction electrons (represented by yellow balls), and hence causes the topological Hall effect (transverse drift of the current). Furthermore, the electric current itself can drive the skyrmion. The critical current density for the drive of skyrmions is around 100 A/cm², by five orders of magnitude smaller than the conventional value for the drive of magnetic domain walls. These features may favor the application of skyrmions to innovative spintronics, i.e. toward “skyrmionics”.

Skyrmion and conduction electron motion

Members

Yoshinori Tokura	Group Director	tokura[at]riken.jp
Masamichi Nakajima	Senior Research Scientist
Chieko Terakura	Senior Technical Scientist	terakura[at]riken.jp
Yoshio Kaneko	Research Consultant
Masakazu Ichikawa	Research Consultant
Yasushi Ogimoto	Senior Visiting Scientist

Publications

K. Ueda, T. Yu, M. Hirayama, R. Kurokawa, T. Nakajima, H. Saito, M. Kriener, M. Hoshino, D. Hashizume, T.-h. Arima, R. Arita, and Y. Tokura

Colossal negative magnetoresistance in field-induced Weyl semimetal of magnetic half-Heusler compound

Nat. Commun. 14, 6339 (2023)
T. Hori, N. Kanazawa, M. Hirayama, K. Fujiwara, A. Tsukazaki, M. Ichikawa, M. Kawasaki, and Y. Tokura

A Noble-Metal-Free Spintronic System with Proximity-Enhanced Ferromagnetic Topological Surface State of FeSi above Room Temperature

Adv. Mater. 35, 2206801 (2022)
A. Kitaori, N. Kanazawa, T. Yokouchi, F. Kagawa, N. Nagaosa, and Y. Tokura

Emergent electromagnetic induction beyond room temperature

Proc. Natl. Acad. Sci. U.S.A. 118, e2105422118 (2021)
T. Yokouchi, F. Kagawa, M. Hirschberger, Y. Otani, N. Nagaosa, and Y. Tokura

Emergent electromagnetic induction in a helical-spin magnet

Nature 586, 232 (2020)
T. Kurumaji, T. Nakajima, M. Hirschberger, A. Kikkawa, Y. Yamasaki, H. Sagayama, H. Nakao, Y. Taguchi, T.-h. Arima, and Y. Tokura

Skyrmion lattice with a giant topological Hall effect in a frustrated triangular-lattice magnet

Science 365, 914 (2019)

Articles

Aug 19, 2021RIKEN RESEARCH Electron–electron and spin–orbit interactions compete to control the electron

The interactions that compete to control electron spin can give rise to novel electronic states useful for future quantum technologies
Jul 17, 2020RIKEN RESEARCH Skyrmions created in a centrosymmetric material lacking geometrical frustration

Tiny magnetic swirls can form in a broader range of materials than have been used in previous experiments
Sep 02, 2019RIKEN RESEARCH Topological superconductivity studied in thin films

A composite material reveals the relationship between superconductivity and exotic electronic states that could be useful in quantum computers
Oct 19, 2018RIKEN RESEARCH Anomalous Hall effect tested in defect-free thin-film magnetic semiconductor

An improved understanding of why electrons take a curved path through magnetic materials could aid the design of the electronic devices of tomorrow
Apr 20, 2018RIKEN RESEARCH Electrical pulses shift the boundaries between magnetic patterns

Electricity can be used to control magnetic patterns in an alloy, opening up the possibility of using them in high-performance devices
Apr 13, 2018RIKEN RESEARCH Anomalous and topological Hall effects can be controlled by an electric field

Controlling the anomalous and topological Hall effects by applying an electric field could lead to new types of memory and logic devices
Mar 16, 2018RIKEN RESEARCH Domain walls allow dissipationless chiral edge conduction of electrons

Chiral edge states could offer a way to store and manipulate information in low-power electronic devices
Mar 02, 2018RIKEN RESEARCH Axion insulator exhibits giant magnetoresistance at low magnetic fields

The resistance of a new design of quantum material varies greatly with magnetic field, making it useful for novel devices
Feb 23, 2018RIKEN RESEARCH Chiral magnets show bulk diode effect due to spin fluctuation

Materials with left- and right-handed responses to current exhibit an intriguing diode effect
Dec 08, 2017RIKEN RESEARCH Solar cells with a quantum shift

A quantum-mechanical way of generating photocurrents may help solar devices overcome existing inefficiencies
Oct 20, 2017RIKEN RESEARCH Positive result for cuprate superconductor

High-temperature superconductivity may be linked to the low-energy pairing of holes on oxygen sites
Feb 03, 2017RIKEN RESEARCH Magnetic bubbles pop up

Skyrmionic bubbles, a potential data carrier in low-energy computing systems, can be controlled using temperature or a magnetic field
Nov 18, 2016RIKEN RESEARCH Switched-on skyrmions

A lattice of magnetic vortices can be created or destroyed simply by applying an electric field
Jan 29, 2016RIKEN RESEARCH A better foundation for 3D memory

The discovery of metal-like domain walls in magnetic insulators may help realize energy-efficient memory devices with massive storage capacities
Jan 15, 2016RIKEN RESEARCH Defrosting a magnetic mystery

An intriguing quantum effect that is potentially useful for practical electronic devices has been realized at significantly higher temperatures than previously observed
Sep 25, 2015RIKEN RESEARCH A magnetic memory bubbling with opportunity

Ultrafast laser pulses can manipulate ‘bubble’ domains for future spintronic and logic devices
May 18, 2015RIKEN RESEARCH Flicking the switch on spin-driven devices

Compressing magnetically and electrically active crystals in one direction unlocks exotic spintronic switching activity
Mar 09, 2015RIKEN RESEARCH Skyrmions get a sonic touch

The use of sound waves to probe nanoscale magnetic whirls called skyrmions could help to develop next-generation memory and data storage technology
Oct 28, 2014RIKEN RESEARCH Multiplying solar harvests with ‘correlated’ technology

Strongly interacting electrons turn oxide interfaces into magnetically controlled and extra-efficient solar cells
Oct 17, 2014RIKEN RESEARCH Putting quantum forces on the map

Mapping the relationship between two quantum effects in materials known as topological insulators could facilitate the development of quantum-based, low-power electronics
Oct 17, 2014RIKEN RESEARCH Light finds a one-way street

A multiferroic material displays a novel spin structure that allows light to travel in only one direction
Aug 08, 2014RIKEN RESEARCH Boosting microelectronics with a little liquid logic

The combination of ferroelectric crystal and ionic liquid could lead to a new class of transistor for fast, low-power memory and logic devices
Mar 14, 2014RIKEN RESEARCH An exotic phase to manipulate spin

In conducting materials, free electrons can move from one point to another, conveying their electrical charge to produce an electrical current. Electrons have another property, known as spin, tha ....