Ultrahigh-resolution photoemission study of superconductors
and strongly correlated materials using quasi-CW VUV laser

Shik Shin

Institute for Solid State Physics, Tokyo University, Kashiwa, 277-8581 Chiba, Japan

We developed the ultrahigh-resolution photoemission system using quasi-CW VUV laser. VUV laser was newly developed for high resolution photoemission. Its photon energy is about 7 eV with 0.26 meV line width and repetition rate is around 80 MHz. The photon energy of 7eV is the highest photon energy as a quasi CW laser. The intensity is quite high with 10(+15) photons/s. We used newly designed ultrahigh resolution photoelectron analyzer (Scienta R4000). The total resolution of the Laser-PES system is estimated to be about 0.36 meV by using the gold Fermi edge at 3 K. We will present several photoemission results on superconducting materials, such as CeRu2, Nb, MgB2 and doped diamond. We found that these superconductors have anisotropic and/or multiple superconducting gaps. Furthermore, we will discuss on the bulk sensitivity of the laser photoemission for the several strongly-correlated materials, such as SrVO3, FeSi, and LiV2O4.