Soft X-ray ARPES study on heavy fermions

Fujimori, Shinichi   ; Okochi, Takuo*; Kawasaki, Ikuto  ; Takeda, Yukiharu   ; Okane, Tetsuo  ; Saito, Yuji  ; Fujimori, Atsushi; Yamagami, Hiroshi; Haga, Yoshinori   ; Yamamoto, Etsuji  ; Onuki, Yoshichika

Recent remarkable progress in ARPES experiments with high energy soft X-ray synchrotron radiation (SX-ARPES) made it possible to directly observe the bulk electronic structure of strongly correlated materials. We have been performing SX-ARPES experiments using SPring-8 BL23SU to understand their electronic structures. In this talk, I will review our recent SX-ARPES studies on heavy Fermion uranium compounds including uranium based superconductors. The results on the heavy Fermion superconductor UPdAl and UNiAl will be presented. It was found that quasi-particle bands with strong U 5 character form Fermi surface at low temperatures, suggesting that U 5 electrons have itinerant nature in these compounds. On the other hand, above the characteristic temperature , U 5 states are excluded from Fermi surface, and they become more localized states. These results were compared with those calculated by the band structure calculation.