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Associate Professor

MATSUDA,
Iwao

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We develop experimental techniques using vacuum ultraviolet ~ soft X-ray, generated by high brilliance synchrotron radiation, X-ray free electron laser (XFEL), and high-harmonic generation (HHG) laser, to reveal physical properties of single atomic layers and surface/interface systems. At SPring-8 BL07LSU, we operate the segmented cross undulator and develop the novel magneto-optical experimental technique using its function of the fast polarization switching. With XFEL and a HHG laser, ultrafast spin dynamics of magnetic ultrathin films and interface layers are investigated by time-resolved measurements of the resonant magneto-optical Kerr effect. At the time-resolved spectroscopy station in SPring-8 BL07LSU, time-resolved measurements of photoemission and X-ray absorption spectroscopy were made with laser and synchrotron radiation. Through the joint-researches of catalysis and photovoltaics, dynamics of carriers and molecules at the surface/interface are studied. We also investigate functionalities in novel monatomic layers such as borophene. With the temporal information collected by individual light sources at each time scale, ranging from femtoseconds to milliseconds, we promote understanding of the whole dynamic picture by combining the sequential information.

Overview of the time-resolved photoemission system at high-brilliant soft X-ray beamline, SPring-8 BL07LSU. Synchrotron radiation pulses, generated at an undulator, pass through a monochromator that is composed of mirrors (M) and a plane-grating (PG). A Ti:Sapphire laser system (BL07LASER) is installed at the beamline.

Time-resolved measurement of the resonant magneto-optical Kerr effect of the ferrimagnetic metallic GdFeCo alloy. (a) Experimental results (circles) of the intensity variation with rotation angle (ellipsometry) taken at hv = 53 eV for soft X-ray FEL at each delay time shown in each figure with fitting by cosine curve (solid lines). Red and blue colored data were taken at the opposite directions of magnetic field. (b) A schematic diagram of the magnetization reversal dynamics of the Fe magnetic moment with respect to an external field H. The length of the arrows is scaled to the magnitude of the Kerr rotation angle at each delay time shown in (a). One can recognize reversal of the Fe spin in the femtosecond-time scale.