We study the electronic structure of strongly correlated electron materials such as high-temperature superconductors with ultrahigh-resolution angle-resolved photoemission spectroscopy (ARPES). ARPES is a unique and powerful experimental technique to directly observe the momentum-resolved electronic structure. We have constructed an ultrahigh-resolution ARPES spectrometer in our laboratory and the present energy resolution is in the world-best level.

Ongoing researches:

• (1) The electronic states of graphane (single-layer graphite) and graphite intercalation compounds, in particular, Dirac-fermion-like behavior in graphene.
• (2) The electronic structure and mechanism of copper-oxide and iron-based high-temperature superconductors, in particular, the “”quasiparticle”” relevant to the origin of superconductivity.
• (3) Construction and improvement of a spin-resolved ultrahigh-resolution photoemission spectrometer and electronic states of spintronics-related materials such as topological insulators.
• (4) Peculiar electronic states at the interface/surface of oxides and semimetals.
• (5) The charge-density wave (CDW), superconductivity, and spin-charge separation in metallic quantum wires and ultrathin films.