Direct observation of the Ce 4f states in the Kondo semiconductor CeRhAs and related compounds:: A high-resolution resonant photoemission study -: art. no. 155202

Ce 4f derived states at the Fermi level (E-F) of the isostructural single crystals CeRhAs, CeRhSb, and CePtSn were observed directly by means of high-resolution (DeltaE=18-20 meV), low-temperature (10-12 K) photoemission spectroscopy with a photon energy of hnu=126 eV. The Ce 4f spectrum for the Kondo semiconductor CeRhAs exhibited no peak structure near E-F, and its spectral intensity decreases monotonically above the binding energy similar to90 meV, thereby forming a large gap structure. The spectrum of the semimetal CeRhSb is enhanced above similar to120 meV, but decreases steeply above similar to13 meV, which indicates the existence of a narrow pseudogap at E-F. A clear crystal field excitation at similar to27 meV, and a weak Kondo resonance at E-F, were found in the metal CePtSn.