Observation of bulk band dispersions of YbRhSi using soft X-ray angle-resolved photoemission spectroscopy

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

We have performed soft X-ray angle-resolved photoemission spectroscopy (ARPES) measurements on YbRhSi and clarified its three-dimensional bulk valence-band structures. The ARPES spectra have not only Yb multiplet peaks but also a finite contribution of Yb peaks at 15 K, corresponding to the valence fluctuating behavior in this compound. This means that Yb 4f electrons in this compound have itinerant character below the . We have found that dispersions of the valence bands except the vicinity of the Yb 4f bands agree better with those of the band-structure calculation of LuRhSi than those of YbRhSi within a local-density approximation. In addition, the Yb 3d-4f resonant photoemission spectra of YbRhSi strongly suggest the existence of Yb 5d electrons in the valence band. We conclude that the charge transfer from the Yb 4f state to the Yb 5d state has an important role in the formation of the valence band of YbRhSi.