Hybridization gap formation in Kondo insulator YbB12 observed using time-resolved photoemission spectroscopy

was revealed by a synergeticcombination of ultrahigh-resolution laser photoemission spectroscopy (PES) and time-resolved PES.The former confirmed a 25-meV pseudogap corresponding to the Kondotemperature of this material,and more importantly, it also revealed that a 15-meV pseudogap and a Kondo-peak feature developedbelow a crossover temperature T