Novel behaviors in rare-earth-filled skutterudites studied by bulk-sensitive photoemission spectroscopy

The electronic structures of rare-earth-filled skutterudites have been investigated by high-resolution photoemission spectroscopy. In order to reveal their bulk nature, the bulk-sensitive photoemission spectroscopy with soft X-ray (hv∼800 – 1100 eV) and hard X-ray (hv∼8000 eV) is a very powerful tool since the rare-earths' valence and electronic structures on the surface are often different from those in the bulk. Our experimental results clearly show the coexistence of the strongly mixed-valence state and the heavy-fermion state in SmOs4Sb12 and the quasi-particle peak near the Fermi level in PrFe4P12 induced by the hybridization between the rare-earth 4f and conduction electrons.