Observation of a kink in the dispersion of f-electrons

Abstract

Strong interactions in correlated electron systems may result in the formation of heavy quasiparticles that exhibit kinks in their dispersion relation. Spectral weight is incoherently shifted away from the Fermi energy, but Luttinger's theorem requires the Fermi volume to remain constant. Our angle-resolved photoemission study of USb2 reveals a kink in a noncrossing 5f band, representing the first experimental observation of a kink structure in f-electron systems. The kink energy scale of 21 meV and the ultra-small peak width of 3 meV are observed. We propose the novel mechanism of renormalization of a point-like Fermi surface, and that Luttinger's theorem remains applicable.