Strong Correlation Interface Research Group

Principal Investigator

PI Name Masashi Kawasaki
Degree D.Eng.
Title Group Director
Brief Resume
1989D.Eng., University of Tokyo
1989Postdoctoral Fellow, Japan Society for the Promotion of Science
1989Postdoctoral Fellow, T. J. Watson Research Center, IBM, USA
1991Research Associate, Tokyo Institute of Technology
1997Associate Professor, Tokyo Institute of Technology
2001Professor, Tohoku University
2007Team Leader, Functional Superstructure Team, RIKEN
2010Team Leader, Strong-Correlation Interfacial Device Research Team, RIKEN
2011Professor, University of Tokyo
2013Deputy Director, RIKEN Center for Emergent Matter Science (CEMS) (-present)
2013Group Director, Strong Correlation Interface Research Group, Strong Correlation Physics Division, RIKEN CEMS (-present)

Outline

Thin films and interfaces of topological materials are the playground of our research. Chiral spin textures in real space and magnetic monopoles in momentum space are the sources of non-trivial Hall effect. Photo-excited polar crystals generate unconventional photocurrent. Not classical mechanics but quantum mechanics is needed to understand those examples. We will design and demonstrate possible devices that utilize expectedly dissipationless electron flow exemplified as above. The device physics study will open a new avenue towards topological electronics that manage flow of information and energy carried by such topological current.

Research Fields

Physics, Engineering, Chemistry, Materials Sciences

Keywords

Topological electronics
Thin films and interfaces
Topological materials
Unconventional photovoltaic effect
Unconventional Hall effect

Results

Observation of shift current photovoltaic effect in an organic ferroelectric compound

Noncentrosymmetric crystals show spontaneous current by photoexcitation. The origin of this phenomenon is theoretically revealed to be the shift current driven by the Berry phase of the Bloch wave function. Recently, shift current attracts attention due to its topological origin as well as the large potential for applications in solar cells and photo-detectors. Here, we focus on an electronic ferroelectric, a material showing a spontaneous polarization dominantly originates from the displacement of electron clouds, as a candidate material showing large shift current. An organic charge transfer complex TTF-CA is one of the representative electronic ferroelectrics. In addition, this compound has a large response to visible and infrared light due to the narrow bandgap of 0.5 eV. We observed a sizable zero-bias photocurrent in TTF-CA below the ferroelectric transition temperature under simulated solar radiation. The current density is larger by several orders compared to other ferroelectric compounds. We also revealed that the zero-bias photocurrent propagates quite a long distance by means of local photoexcitation. This is a clear evidence for the non-local nature of shift current.

Schematic of shift current generation in an organic ferroelectric TTF-CA

Members

Masashi Kawasaki

Group Director m.kawasaki[at]riken.jp R
Kei Takahashi Senior Research Scientist kei.takahashi[at]riken.jp R

Masao Nakamura

Senior Research Scientist masao.nakamura[at]riken.jp R

Denis Maryenko

Research Scientist maryenko[at]riken.jp

Yusaburo Segawa

Research Consultant
Jobu Matsuno Visiting Scientist R

Articles

お問い合わせ

  

TEL:+81-(0)48-467-9604

E-mail:
m.kawasaki[at]riken.jp

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