Photoemission Study of Mixed-Valent Tm-monochalcogenides: Evidence of Electron-Correlation Effect in Different Tm-Core Levels

Abstract

Systematic results of the photoemission spectra for different core levels such as, Tm 4 p , 5 p and 3 d in the mixed valent Tm-monochalcogenides (TmS, TmSe and TmTe) obtained by both experimentally and theoretically are reported. The effects of the electron–electron correlation due to the interaction between core-holes and 4 f -electrons or the interaction between different configurations are considered to explain the spectral features, depending on the principal ( n ) and orbital quantum numbers of the core levels. Any sharp peak corresponding to a spin–orbital term is not observed especially from the n =4 states. Instead, the multiplet structures are dominantly observed, and the physical identity of the spin–orbital peaks is totally or partially dissolved into the multiplets. Moreover, the electron-correlation effect is found to be dependent on the valence components (Tm 2+ and Tm 3+ ). In the case of the Tm 4 p core level, in which the principal quantum number is identical with the valence 4 f , the co...