Observation of Kondo resonance in rare-earth hexaborides using high resolution photoemission spectroscopy

We studied the electronic structure of rare earth hexaborides, CeB6, PrB6 and NdB6 using state-of-the-art high resolution photoemission spectroscopy. CeB6 is a dense Kondo system. PrB6 and NdB6 are antiferromagnetic (Neel temperature similar to 7 K), known to be stable moment systems and do not exhibit Kondo effect. Photoemission spectra exhibit distinct signature of surface and bulk electronic structures of these compounds. The energy position of the surface feature is not influenced by the 4f density of states. High resolution spectra of CeB6 reveal multiple Kondo resonance features in the bulk spectra due to various photoemission final states. Interestingly, high resolution photoemission spectra of antiferromagnetic PrB6 also exhibit a sharp feature at the Fermi level that shows temperature dependence similar to the Kondo resonance features.