Mechanism of superconductivity in the polyhedral-network compound Ba8Si46
Mechanism of superconductivity in the polyhedral-network compound Ba8Si46
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DOI：
10.1038/nmat981
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发表时间：
2003-10
期刊：
影响因子：
41.2
通讯作者：
K. Tanigaki;K. Tanigaki;T. Shimizu;K. Itoh;K. Itoh;J. Teraoka;Y. Moritomo;Y. Moritomo;S. Yamanaka
中科院分区：
文献类型：
--
作者：
K. Tanigaki;K. Tanigaki;T. Shimizu;K. Itoh;K. Itoh;J. Teraoka;Y. Moritomo;Y. Moritomo;S. Yamanaka
硅笼形物-由金属掺杂的Si 20十二面体组成的材料-被认为是第一个基于纯硅网络的超导体。这些材料的超导机制可以通过研究它们的声子模式来获得，通过同位素替代和比热测量来修改。在这里，我们目前的实验研究提供了强有力的证据，在Ba 8 Si 46的超导性是在声子介导的Bardeen-Cooper-Schriefer理论的框架内解释。利用Eliashberg方程的McMillan近似分析表明，超导机制处于介质耦合状态，但处于高端极限。由于Si 20团簇和Ba轨道的杂化，费米能级处的态密度很大，这是导致超导温度意外高的原因。比热的温度演化明确地表明这是一个s波对称超导体。
The silicon clathrates—materials composed of metal-doped Si20dodecahedra—were identified as the first superconductors based on pure silicon networks,. 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 Ba8Si46is explained in the framework of phonon-mediated Bardeen–Cooper–Schriefer theory. Analyses using the McMillan approximation,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 Si20cluster 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.