Electronic structure of Yb-based compounds studied by soft X-ray angle-resolved photoemission spectroscopy

Yasui, Akira; Fujimori, Shinichi   ; Kawasaki, Ikuto  ; Okane, Tetsuo  ; Takeda, Yukiharu   ; Saito, Yuji  ; Sekiyama, Akira*; Settai, Rikio*; Lapertot, G.*; Knebel, G.*; Matsuda, Tatsuma; Haga, Yoshinori   ; Yamagami, Hiroshi; Onuki, Yoshichika*

We have performed SX-ARPES measurements to investigate 3D valence-band dispersions in the bulk state of YbCuGe, YbCuSi, and YbRhSi. It had been thought that YbCuGe is an Yb divalent compound. On the contrary, our SX-ARPES study of YbCuGe clarified that Yb 4 electrons contribute to the formation of FSs through the hybridization with conduction bands, as observed in the typical valence fluctuating compound YbCuSi. The 3D band structures of YbCuGe can be reasonably explained by a relativistic LDA calculation, while those of YbCuSi and the nearly trivalent compound YbRhSi cannot be explained by it. Especially the relativistic LDA calculation of LuRhSi can describe the observed band dispersions of YbRhSi rather than that of YbRhSi. In the presentation, we will discuss the valence band structures obtained by the SX-ARPES measurements in term of the Yb valence systematically.