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Okazaki Group

Associate Professor OKAZAKI, Kozo
Research Associate SUZUKI, Takeshi

Research Subjects

  • Development of a time-resolved photoemission apparatus utilizing high harmonic generation from a ultrashort-pulse laser
  • Mechanisms of electron relaxation from photo-excited states and light-induced superconductivity
  • Mechanisms of unconventional superconductivities by ultralow temperature and ultrahigh resolution laser-based angle-resolved photoemission spectroscopy

Angle-resolved photoemission spectroscopy is a very powerful experimental technique that can directly observe a dispersion relation between momentum and energy (band structure) of the electrons in solid-state materials, whereas by utilizing a femtosecond laser as pumping light and its high harmonic generation (HHG) as probing light, we can observe ultrafast transient properties of the band structure in a non-equilibrium state. In our group, we are developing and improving a time-resolved photoemission apparatus that utilizes high harmonic generation of an ultrashort-pulse laser in collaboration with laser development groups, and aiming for understanding the mechanisms of electron relaxation dynamics from photo-excited states and demonstration of photo-induced superconductivity by direct observations of transient electronic states using pump-probe type time-resolved photoemission spectroscopy (TRPES). In addition, we are aiming for understanding the mechanisms of unconventional superconductivity by direct observations of the electronic structures and superconducting-gap structures of unconventional superconductors with a laser-based angle-resolved photoemission apparatus with a world-record performance that achieves a maximum energy resolution of 70 μeV and lowest cooling temperature of 1 K.

Schematic diagram of a time-resolved photoemission apparatus utilizing a femtosecond laser and its high harmonic generation.
Photo-induced insulator-to-metal transition in an excitonic insulator Ta2NiSe5 observed by HHG laser TRPES. a, b. Spectra before and after pump, respectively.

Publications and Research Highlights