Dynamic Emergent Phenomena Research Team

Principal Investigator

PI Name Fumitaka Kagawa
Degree D. Eng.
Title Team Leader
Brief Resume
2006 D.Eng., University of Tokyo
2006 Research fellowship for young scientists
2007 Researcher, JST-ERATO Multiferroic project
2010 Project Lecturer, Quantum-Phase Electronics Center, University of Tokyo
2012 Lecturer, Department of Applied Physics, University of Tokyo
2013 Unit Leader, Dynamic Emergent Phenomena Research Unit, Cross-Divisional Materials Research Program, RIKEN Center for Emergent Matter Science
2017 Associate Professor, Department of Applied Physics, University of Tokyo
2022 Professor, Department of Physics, Tokyo Institute of Technology  (-present)
2022 Team Leader, Dynamic Emergent Phenomena Research Team, RIKEN Center for Emergent Matter Science (-present)

Outline

Our team explores dynamic phenomena exhibited by strongly correlated electron systems in both bulk and device structures to construct a new scheme for scientific investigation. In particular, we study external-field-driven dynamic phenomena exhibited by sub-micron-scale structures, such as topological spin textures and domain walls, using spectroscopy of dielectric responses and resistance fluctuations from the millihertz to gigahertz region. We also pursue real-space observations and measurements of local physical properties using scanning probe microscopy as a complementary approach. We are aiming to control novel physical properties exhibited by topological structures in condensed matter systems on the basis of knowledge obtained from these methods.

Research Fields

Physics, Materials Science

Keywords

Strongly correlated electron system
Phase control
Scanning probe microscopy
Spectroscopy

Results

Kinetic approach to superconductivity hidden behind a competing order

In strongly correlated electron systems, the emergence of superconductivity is often inhibited by the formation of a thermodynamically more stable magnetic/charge order. Nevertheless, by changing thermodynamic parameters, such as the physical/chemical pressure and carrier density, the free-energy balance between the superconductivity and the competing order can be varied, thus enabling the superconductivity to develop as the thermodynamically most stable state. We demonstrate a new kinetic approach to avoiding the competing order and thereby inducing persistent superconductivity. In the transition-metal dichalcogenide IrTe2 as an example, by utilizing current-pulse-based rapid cooling up to ~107 K s‒1, we successfully kinetically avoid a first-order phase transition to a competing charge order and uncover metastable superconductivity hidden behind. The present method also enables non-volatile and reversible switching of the metastable superconductivity with electric pulse applications, a unique advantage of the kinetic approach. Thus, our findings provide a new approach to developing and controlling superconductivity.

Figure

Conceptual phase diagram of superconductivity with ultra-rapid cooling (left), the thin-plate sample used in the experiments (top right) and non-volatile switching between superconducting and non-superconducting states demonstrated by resistivity measurements (bottom right)

Members

Fumitaka Kagawa

 Team Leader fumitaka.kagawa[at]riken.jp

Tetsuya Nomoto

 Postdoctoral Researcher

Hiroshi Oike

 Visiting Scientist

Takuro Sato

 Visiting Scientist

Keisuke Matsuura

 Visiting Scientist

Publications

  1. T. Sato, W. Koshibae, A. Kikkawa, Y. Taguchi, N. Nagaosa, Y. Tokura, and F. Kagawa

    Nonthermal current-induced transition from skyrmion lattice to nontopological magnetic phase in spatially confined MnSi

    Phys. Rev. B 106, 144425 (2022)
  2. H. Oike, K. Takeda, M. Kamitani, Y. Tokura, and F. Kagawa

    Real-Space Observation of Emergent Complexity of Phase Evolution in Micrometer-Sized IrTe2 Crystals

    Phys. Rev. Lett. 127, 145701 (2021)
  3. K. Matsuura, H. Oike, V. Kocsis, T. Sato, Y. Tomioka, Y. Kaneko, M. Nakamura, Y. Taguchi, M. Kawasaki, Y. Tokura, and F. Kagawa

    Kinetic pathway facilitated by a phase competition to achieve a metastable electronic phase

    Phys. Rev. B 103, L041106 (2021)
  4. H. Oike, M. Kamitani, Y. Tokura, and F. Kagawa

    Kinetic approach to superconductivity hidden behind a competing order

    Sci. Adv. 4, aau3489 (2018)
  5. H. Oike, A. Kikkawa, N. Kanazawa, Y. Taguchi, M. Kawasaki, Y. Tokura, and F. Kagawa

    Interplay between topological and thermodynamic stability in a metastable magnetic skyrmion lattice

    Nat. Phys. 12, 62 (2016)

Articles

お問い合わせ

2-1 Hirosawa, Wako, Saitama 351-0198 Japan

E-mail：
fumitaka.kagawa[at]riken.jp

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