Photoemission study of the skutterudite compounds CoSb3 and RhSb3

We have studied the electronic structure of the skutterudite compounds CoSb 3 and Co(Sb 0.96 Te 0.04 ) 3 by photoemission spectroscopy. Valence-band spectra revealed that a significant amount Sb 5 p states are present near the Fermi level and are hybridized with Co 3 d states just below it. The spectra are well reproduced by the band-structure calculation, suggesting that the effect of electron correlations is not important. When Te is substituted for Sb and n -type carriers are doped into CoSb 3 , the spectra are shifted to higher binding energies as described by the rigid-band model. From this shift and the free-electron model for the conduction and valence bands, we have estimated the band gap of CoSb 3 to be 0.03–0.04 eV, consistent with transport measurements. Photoemission spectra of RhSb 3 have also been measured and revealed expected similarities to and differences from those of CoSb 3 . Unusual temperature dependence has been observed for the spectra of CoSb 3 and RhSb 3 in the vicinity of the Fe...