부산대학교 도서관

We report the results of angle-resolved photoemission spectroscopy (ARPES) on the Sm1−xYxSsystem, which exhibits a black-to-golden phase transition induced by yttrium substitution and by anapplied external pressure, in order to investigate the mechanism of this transition and the electronicstructure of both phases. The obtained ARPES spectrum of pure SmS (x = 0) indicates a bandinsulator, in which the shallowest electronic state is the Sm2+ 4f state at a binding energy of about0.4 eV. With increasing x, the top of the Sm2+ 4f band shifts to the lower binding energy side andtouches the Fermi level for x = 0.33. Because of the discontinuous reduction of the lattice constantin the vicinity of the black-to-golden phase transition (x 0.17), the golden phase induced byyttrium substitution is concluded to be an intermediate valence state.