The electronic structure of Ca-intercalated superconducting graphite CaC6 |
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| Authors: | H. Okazaki R. Yoshida K. Iwai K. Noami T. Muro T. Nakamura T. Wakita Y. Muraoka M. Hirai F. Tomioka Y. Takano A. Takenaka M. Toyoda T. Oguchi T. Yokoya |
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| Affiliation: | 1. The Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan;2. Japan Synchrotron Radiation Research Institute (JASRI)/SPring-8, Hyogo 679-5198, Japan;3. Research Laboratory for Surface Science (RLSS), Okayama University, Okayama 700-8530, Japan;4. JST, CREST, 3-1-1 Tsushima-naka, Okayama 700-8530, Japan;5. National Institute for Materials Science (NIMS), Tsukuba, Ibaraki 305-0047, Japan;6. Faculty of Engineering, Oita University, Oita 870-1192, Japan;7. Department of Quantum Matter, Graduate School of Advanced Sciences of Matter (ADSM), Higashi-Hiroshima, Hiroshima 739-8530, Japan |
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| Abstract: | We have measured Ca-intercalated graphite superconductor CaC6 (Tc = 11.2 K) by soft X-ray photoemission spectroscopy in order to understand the electronic structure. For the valence band, we observed several structures that correspond to those of calculated density of states with the partial density of states of Ca 3d at the Fermi level (EF). We also observed core level spectra that are a very large asymmetric Ca 2p and asymmetric C 1s for CaC6, suggesting the existence of conduction electrons derived from Ca 3d and a charge transfer from Ca to graphene layer. These results provide spectroscopic evidence for PDOS of Ca 3d at EF. From a comparison of electronic structure of CaC6 and other graphite intercalation compounds (GICs), we found the difference between CaC6 and other superconducting GICs, which provides deeper understanding of the superconductivity of CaC6. |
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| Keywords: | Graphite intercalation compounds Soft X-ray photoemission spectroscopy Electronic structure |
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