Emergent Photodynamics Research Unit

Principal Investigator

PI Name Naoki Ogawa
Title Unit Leader
Brief Resume
2004D.Eng., University of Tokyo
2004Postdoctoral Associate, University of California at Irvine
2004Research Fellow of the Japan Society for the Promotion of Science
2006Project Assistant Professor, University of Tokyo
2008Assistant Professor, University of Tokyo
2012ASI Research Scientist, RIKEN
2013Senior Research Scientist, RIKEN Center for Emergent Matter Science
2015Unit Leader, Emergent Photodynamics Research Unit, Cross-Divisional Materials Research Program, RIKEN Center for Emergent Matter Science (-present)

Outline

Our research unit explores novel photodynamics of electron/spin in bulk crystals and at thin-film interfaces emerging via electron-correlation and strong spin-orbit interactions. Examples are the spin current generation mediated by photoexcited Dirac electrons and the ultrafast coherent control/spectroscopy of topological spin textures. With a strong command of photons, we try to realize new photomagnetic effects in solids, and visualize the spatiotemporal propagation of elementally excitations at the sub-diffraction limit.

Research Fields

Physics, Engineering, Materials Sciences

Keywords

Strongly correlated electron system
Spin-orbit interaction
Ultrafast spectroscopy
Spintronics

Results

Photoinduced dynamics in topological spin textures

High-speed magnetic memories and photonic-magnonic interconnections will be realized by using the pulsed-optical-control of spins. For this purpose, the inverse-Faraday effect, one of the optomagnetic phenomena, is promising, where circularly-polarized laser pulses at non-absorbing photon energy can induce effective magnetic fields via strong spin-orbit interactions. We demonstrated that the collective dynamics of magnetic skyrmions, topologically-protected nano-scale spin vortices, can be characterized by using the inverse-Faraday excitation and time-resolved magneto-optics with sub-picosecond time-resolution. We also found that magnetoelastic waves, coupled propagation of magnon and phonon, can be excited in iron garnet films by photoexcitation. The time-resolved microscopy on the magnetoelastic wave revealed that this traveling spin excitation shows an attractive interaction with magnetic bubbles (skyrmions) and domain walls, whose efficiency strongly depends on the curvature of the local spin texture.

(a) Schematics for the impulsive Raman excitation.
(b) Rotation dynamics of magnetic skyrmions in Cu2OSeO3.
(c) Magneto-optical microscopy on photoexcited magnetoelastic waves.
(d) Optical manipulation of a magnetic bubble domain.

Members

Naoki Ogawa

Unit Leader naoki.ogawa[at]riken.jp

Masato Sotome

Postdoctoral Researcher

Shingo Toyoda

Postdoctoral Researcher

Articles

お問い合わせ

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

E-mail:
naoki.ogawa[at]riken.jp

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