Spectral Evidence for Pseudogap Formation in Kondo Insulators CeRhAs and CeRhSb

Abstract

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 while it is gradually filled with increasing temperature. The size of the pseudogap is well scaled with the Kondo temperature $({T}_{K})$ of each compound while the temperature evolution is dominated by another characteristic temperature ${T}_{\mathrm{coh}}$ $(<{T}_{K})$. The results are qualitatively consistent with the theoretical prediction from the Anderson lattice model.