Direct observation of heavy quasiparticles in the Kondo-lattice compound CeI n3

The electronic structure of the Kondo lattice CeI n₃ has been studied by on-resonant angle-resolved photoemission spectroscopy and scanning tunneling microscopy/spectroscopy. A weakly dispersive quasiparticle band has been observed directly with an energy dispersion of 4 meV by photoemission, implying the existence of weak hybridization between the f electrons and conduction electrons. The hybridization is further confirmed by the formation of the hybridization gap revealed by temperature-dependent scanning tunneling spectroscopy. Moreover, we find the hybridization strength in CeI n₃ is much weaker than that in the more two-dimensional compounds CeCoI n₅ and CeIrI n₅ . Our results may be essential for the complete microscopic understanding of this important compound and the related heavy-fermion systems.