We study the electronic structure of strongly correlated electron systems and functional materials such as high-temperature superconductors, topological insulator, and graphene materials 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 (1.3 meV) is in the world-best level.

Fig. 1: Fermi surface and superconducting gap of Bi2Sr2Ca2Cu3O10

Fig2 : Quasipartile dispersion of high-Tc superconductor

On-going researches:

(1) Electronic structure and mechanism of high-temperature superconductors;

in particular, the "quasiparticles" relevant to the origin of superconductivity

Electronic structure of nano graphite materials (graphene, nanotube, GIC etc.)
Mechanism of superconductivity in novel exotic superconductors
Spin-orbit interaction and many-body effect in semi-metal (Sb, Bi, As) surfaces
Kondo-lattice effect in 4f/5f electron materials
Charge-density wave (CDW) and superconductivity in 1D quantum wire and ultrathin film
Construction of a bulk-sensitive spin-resolved ultrahigh-resolution photoemission spectrometer


(1) Ultrahigh-resolution ARPES spectrometer (1st version)
Ultrahigh-resolution ARPES spectrometer (2nd version)
Bulk-sensitive spin-resolved ultrahigh-resolution ARPES spectrometer (under construction)
high-resolution photoemission spectrometer
high-resolution ARPES spectrometer

We also use synchrotron radiation facilities such as "Synchrotron radiation center (SRC)" in Wisconsin, SPring-8, Photon Factory (PF), and UVSOR.

Fig.3: Ultrahigh-resolution photoemission spectrometer