Electronic structure of black SmS. II. Angle-resolved photoemission spectroscopy

We have studied the electronic band structure of semiconducting black SmS with high-resolution angle-resolved photoemission spectroscopy (ARPES). The valence band consists of two well-separated groups of bands: almost nondispersive bands near (formula presented) and highly dispersive bands at higher binding energy. The former is ascribed to the (formula presented) (formula presented) multiplet and the latter to mainly the S (formula presented) states. We found a small but distinct energy dispersion in the Sm (formula presented) This indicates a strong hybridization between the “localized” Sm (formula presented) electrons and the “itinerant” conduction electrons, leading to the “delocalized” Sm (formula presented) states in mixed-valent SmS. We have compared the present ARPES results with a recent periodic Anderson model calculation [C. Lehner et al., Phys. Rev. B 58, 6807 (1998)].