Electronic structure of the Chevrel-phase compounds SnxMo6Se7.5: Photoemission spectroscopy and band-structure calculations - art. no. 195109

We have studied the electronic structure of two Chevrel-phase compounds, Mo 6Se7.5 and Sn1,2Mo6Se7.5, by combining photoemission spectroscopy and band- structure calculations. Core-level spectra taken with x-ray photoemission s pectroscopy show systematic core-level shifts, which do not obey a simple r igid-band model. The inverse photoemission spectra imply the existence of a n energy gap located similar to1 eV above the Fermi level, which is a chara cteristic feature of the electronic structure of the Chevrel compounds. Qua ntitative comparisons between the photoemission spectra and the band-struct ure calculations have been made. While good agreement between theory and ex periment in a wide energy range was obtained as already reported in previou s studies, we found that the high density of states near the Fermi level pr edicted theoretically due to the Van Hove singularity is considerably reduc ed in the experimental spectra taken with higher energy resolution than in previous reports. Possible explanations for this observation are proposed.