Band structure and Fermi surface of heavy fermion superconductors

Fujimori, Shinichi   ; Okochi, Takuo; Okane, Tetsuo  ; Saito, Yuji  ; Fujimori, Atsushi; Yamagami, Hiroshi; Ikeda, Shugo; Matsuda, Tatsuma; Haga, Yoshinori   ; Yamamoto, Etsuji  ; Onuki, Yoshichika*

We have observed the band structures and Fermi surfaces (FS's) of the heavy Fermion (HF) superconductors UPdAl, UNiAl and URuSi by angle-resolved photoemission experiments in soft X-ray region (SX-ARPES). SX-ARPES is a recently developed experimental technique, by which one can observe bulk-sensitive and U 5-dominant band structures and FS's of uranium compounds. We have found quasi-particle bands of U 5 electron origin form Fermi surface at low temperature, suggesting that U 5 electrons have itinerant character in these compounds. On the other hand, above , U 5 electrons are excluded from Fermi surface, and they become localized electrons at high temperatures. The experimental band structures and Fermi surfaces are compared with the results of band structure calculations, and the localized and itinerant natures of U 5 electrons are discussed in terms of their electronic structures.