Exotic superconductivity in strongly anisotropic correlatedorganic metals in the vicinity of insulating phases

序参量在动量空间或真实的空间振荡的非常规超导性有望在强电子关联的导电材料中实现，近年来引起了人们极大的兴趣。有机金属具有许多特性，这使得它们特别有吸引力的模型系统，用于系统地研究超导性和正常金属态的其他不稳定性之间的微妙相互作用。本项目的主要目标是揭示这些材料中奇异超导性的表现及其与其他有序不稳定性的相互作用。选择用于研究的化合物在紧邻甚至与其他有序基态共存的情况下表现出超导性：电荷密度波金属alpha-（ET）2KHg（SCN）4;反铁磁金属kappa-（BETS）2FeCl 4;磁有序（可能是莫特）绝缘体kappa-（BETS）2 Mn [N（CN）2]3。该项目旨在阐明这些化合物的竞争有序对超导（SC）性能的影响。所有这些化合物的有序不稳定性的相对强度对压力敏感。这为研究SC性质对密度波或磁有序的压力控制的依赖性提供了一个方便的机会。由于非常高的电子各向异性，在这些材料中，平行于层的磁场的轨道对断裂效应被强烈抑制。在这种情况下，对电荷载流子的泡利顺磁效应预计将是占主导地位的对断裂机制。如果样品足够干净，这将提供从均匀SC态到Fulde-Ferrell-Larkin-Ovchinnikov（FFLO）态的场诱导跃迁的必要和充分条件，其序参量在真实的空间中振荡。在上述化合物中寻找FFLO态是本项目的另一个主要目标，其中两个化合物具有很低的SC临界温度（约0.1K）。这有利于直接测量的临界场，因为在运输和磁化的涡旋动力学效应，这通常会导致大问题，在准二维超导体，强烈抑制在整个SC范围。该研究项目计划与俄罗斯切尔诺戈洛夫卡的合作伙伴合作，他们将为物理研究提供晶体，并开发新材料，这些材料也将在项目中进行测试。kappa-（BETS）2 Mn [N（CN）2]3的实验也将与俄罗斯合作伙伴合作进行。

Unconventional superconductivity with the order parameter oscillating in momentum or real space, which is expected to be realized in conducting materials with strong electronic correlations, has lately been a subject of great interest. Organic metals possess a number of features, which make them particularly attractive model systems for systematically studying the subtle interplay between superconductivity and other instabilities of the normal metallic state.The main goal of this project is to reveal manifestations of exotic superconductivity and its interplay with other ordering instabilities in these materials. The compounds chosen for studies exhibit superconductivity in the immediate vicinity to and even coexisting with other ordered ground states: the charge-density-wave metal alpha-(ET)2KHg(SCN)4; the antiferromagnetic metal kappa-(BETS)2FeCl4; the magnetically ordered (probably Mott) insulator kappa-(BETS)2Mn[N(CN)2]3. The project aims at clarifying the influence of the competing orderings on superconducting (SC) properties of these compounds. The relative strength of the ordering instabilities in all these compounds is sensitive to pressure. This provides a convenient opportunity for studying the dependence of SC properties on the pressure-controlled proximity to the density-wave or magnetic ordering.Due to the very high electronic anisotropy, the orbital pair-breaking effect of a magnetic field parallel to layers is strongly suppressed in these materials. In this situation the Pauli paramagnetic effect on charge carriers is expected to be the dominant pair-breaking mechanism. If the samples are clean enough, this will provide the necessary and sufficient condition for a field-induced transition from a homogeneous SC state into the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state with an order parameter oscillating in real space. The search for the FFLO state in the above mentioned compounds is another major objective of this project.Two of the chosen compounds are characterized by very low SC critical temperatures (about 0.1K). This facilitates straightforward measurements of the critical fields since the vortex dynamics effects in transport and magnetization, which usually cause big problems in quasi-two-dimensional superconductors, are strongly suppressed in the whole SC range. The research project is planned in cooperation with partners at Chernogolovka, Russia, who will deliver the crystals for the physical investigations and develop novel materials which will also be tested within the project. The experiments on kappa-(BETS)2Mn[N(CN)2]3 will also be conducted in cooperation with the Russian partners.