Letter abstract
Nature Materials 2, 653 - 655 (2003)
Published online: 14 September 2003 | doi:10.1038/nmat981
Subject Category: Superconductors
Mechanism of superconductivity in the polyhedral-network compound Ba8Si46
K. Tanigaki1,2, T. Shimizu3, K. M. Itoh2,3, J. Teraoka1, Y. Moritomo2,4 & S. Yamanaka5
The silicon clathrates—materials composed of metal-doped Si20 dodecahedra—were identified as the first superconductors based on pure silicon networks1, 2. The mechanism of superconductivity in these materials can be obtained by studying their phonon modes, as modified by isotope substitution, and specific-heat measurements. Here, we present experimental studies that provide strong evidence that superconductivity in Ba8Si46 is explained in the framework of phonon-mediated Bardeen–Cooper–Schriefer theory. Analyses using the McMillan approximation3, 4 of the Eliashberg equation indicate that the superconducting mechanism is in the medium coupling regime, but at the high-end limit. The large density of states at the Fermi level, which arises from hybridization of the Si20 cluster and Ba orbitals, is responsible for the unexpectedly high superconducting temperature. The temperature evolution of the specific heat unambiguously shows that this is an s-wave symmetry superconductor.
- Graduate School of Science, Materials Science Osaka City University, 3-3-138, Sugimoto, Sumiyoshi, Osaka 558-8585, Japan
- PRESTO/CREST-JST, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan
- Department of Applied Physics and Physico-Informatics, Keio University, Yokohama 223-8522 Japan
- Department of Applied Physics, Nagoya University, Furo-cho, Chidane-ku, Nagoya 464-8601, Japan
- Department of Applied Chemistry, Hiroshima University, Higashi-Hiroshima 739-8527, Japan
Correspondence to: K. Tanigaki1,2 e-mail: tanigaki@sci.osaka-cu.ac.jp
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