Recent Topics of Organic Superconductors
Recent Topics of Organic Superconductors
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DOI：
10.1143/jpsj.81.011004
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发表时间：
2012-01-01
影响因子：
1.7
通讯作者：
Wosnitza, Jochen
中科院分区：
文献类型：
--
作者：
Ardavan, Arzhang;Brown, Stuart;Wosnitza, Jochen
综述了有机材料超导研究的最新进展。在划时代的准一维 TMTSF 超导体中，T-c 接近 1 K，T-c 随着压力的增加而单调减小，正常状态下自旋涨落的特征也是如此，为磁介导配对提供了良好的证据。上临界场超过塞曼极限场数倍，表明高磁场下存在三重态配对或向非均匀超导态的转变，而核磁共振奈特位移测量在低场下排除了三重态配对。空间不均匀超导态（Fulde-Ferrel-Larkin-Ovchinnikov 态）的证据长期以来一直在各种超导系统中寻找，现在通过清洁和高度二维 BEDT-TTF 和 BETS 超导体的热力学和输运测量获得了证据。一些层状超导体还可以用作各向异性三角晶格莫特物理学的模型系统。例如，能斯特效应和核磁共振弛豫中的赝能隙行为在莫特跃迁附近增强。在自旋挫败增加的情况下，超导转变温度降低，并且在相邻莫特绝缘相中反铁磁有序性被完全消除。越来越多的材料在与电荷序的竞争或合作中表现出超导性。理论研究揭示了在接近有机材料多样性中相关诱导绝缘相的条件下出现的自旋和/或电荷波动对超导性的作用。
Recent developments in research into superconductivity in organic materials are reviewed. In the epoch-defining quasi-one-dimensional TMTSF superconductors with T-c similar to 1 K, T-c decreases monotonically with increasing pressure, as do signatures of spin fluctuations in the normal state, providing good evidence for magnetically-mediated pairing. Upper critical fields exceed the Zeeman-limiting field by several times, suggesting triplet pairing or a transition to an inhomogeneous superconducting state at high magnetic fields, while triplet pairing is ruled out at low fields by NMR Knight-shift measurements. Evidence for a spatially inhomogeneous superconducting state, Fulde-Ferrel-Larkin-Ovchinnikov state, which has long been sought in various superconducting systems, is now captured by thermodynamic and transport measurements for clean and highly two-dimensional BEDT-TTF and BETS superconductors. Some of the layered superconductors also serve as model systems for Mott physics on anisotropic triangular lattice. For example, the Nernst effect and the pseudo-gap behavior in NMR relaxation are enhanced near to the Mott transition. In the case of increasing spin frustration, the superconducting transition temperature is depressed, and antiferromagnetic ordering is eliminated altogether in the adjacent Mott insulating phase. There is an increasing number of materials exhibiting superconductivity in competition or cooperation with charge order. Theoretical studies shed light on the role of spin and/or charge fluctuations for superconductivity appearing under conditions close to those of correlation-induced insulating phases in the diversity of organic materials.