Low-energy excited photoemission spectroscopy of YxYb1−xInCu4

Low-energy excited photoemission spectroscopy (LEPES) has been carried out at hν = 7 eV for the Y-doped YbInCu4, which exhibits a valence transition with the low Y concentration. In the LEPES spectra of YxYb1−xInCu4 (x = 0.1, 0.2), the structure appears at 20-60 meV below the valence transition temperature (TV) and its energy position shifts toward to the Fermi level with increasing x. The energy shift is qualitatively consistent with the decrease of the Kondo temperature below TV suggested from the magnetic susceptibility measurements. The Kondo peak in the high temperature phase is not detected still for x = 0.25 with no valence transition, suggesting also the decreases of the Kondo temperature above TV.