Dynamic Emergent Phenomena Research Unit

Principal Investigator

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


Our unit 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 Sciences


Strongly correlated electron system
Organic ferroelectrics
Scanning probe microscopy


Demonstration of charge/spin phase-change memory function

An aggregation of interacting atoms condenses into either a crystal or non-equilibrium glass depending on cooling speed. Chalcogenide phase-change memory (PCM), a promising candidate for next-generation non-volatile memories, exploits such an atom-configuration degree of freedom as optically or electrically switchable state variables. This unique memory concept has thus far been used exclusively in an aggregation of atoms. Here, we demonstrate a new class of PCM emerging from a charge-configuration degree of freedom in strongly correlated electrons. Reversible switching between a high-resistivity charge-crystalline (or charge-ordered) state and a low-resistivity quenched state, charge glass, is achieved via both optical and electrical thermal quench in organic conductors. Furthermore, on the basis of the similar working principle, we also demonstrate a non-volatile and reversible switching between distinct magnetic orders (conical magnetism and magnetic skyrmion lattice) by using electric pulses. Our results would open a new avenue toward novel PCM functions.

Charge phase-change memory (left) and spin phase-change memory (right)


Fumitaka Kagawa

Unit Leader fumitaka.kagawa[at]riken.jp

Hiroshi Oike

Postdoctoral Researcher hiroshi.oike[at]riken.jp

Takuro Sato

Postdoctoral Researcher



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