Direct observation of pseudogap of SmB6 using ultrahigh-resolution photoemission spectroscopy

We have performed a temperature-dependent ultrahigh-resolution photoemission spectroscopy on SmB6 to study the Kondo-insulator nature. We found a sharp Sm 4f-derived peak about 18 meV away from E-F and a pseudogap at E-F at low temperature. The pseudogap is gradually filled-in by the transfer of spectral weight from the sharp peak at high temperatures. This indicates that the pseudogap is a Kondo-insulator gap originating in the hybridization between the Sm 4f states and the conduction electrons. (C) 2002 Elsevier Science B.V. All rights reserved.