Pseudogap formation in Kondo insulators CeRhSb and CeRhAs studied by ultrahigh-resolution photoemission spectroscopy

We report an ultrahigh-resolution (Delta E similar to 8 meV) temperature-de pendent photoemission spectroscopy on the Kondo insulators CeRhAs and CeRhS b. We have observed a pseudogap at the Fermi level at low temperature for b oth compounds, which is gradually filled-in with increasing temperature. We found that, the, size of pseudogap is well scaled with the Kondo temperatu re (T-K) while the temperature evolution is dominated by another characteri stic temperature much lower than T-K. (C) 2000 Published by Elsevier Scienc e B.V. All rights reserved.