Spectral evidence for pseudogap formation in Kondo insulators CeRhAs and CeRhSb

High-resolution photoemission spectroscopy has been performed on CeRhAs and CeRhSb to study the temperature-induced evolution of the "Kondo-insulator" gap. We have observed that a pseudogap opens at E-F at low temperatures wh ile it is gradually filled with increasing temperature. The size of the pse udogap is well scaled with the Kondo temperature (T-K) of each compound whi le the temperature evolution is dominated by another characteristic tempera ture T-coh (< T-K) The results are qualitatively consistent with the theore tical prediction from the Anderson lattice model.