Materials World Network: Microscopic Study of Inhomogeneous Supeconductivity

这是格勒诺布尔高磁场实验室（GHMFL）和布朗大学之间的合作研究成果。 本研究的总主题是非均匀超导性的微观研究，即，Fulde-Ferrell-Larkin-Ovchinikov（FFLO）状态。对这种现象的研究不仅与凝聚态物理有关，而且与基本粒子和原子物理也有关。在低温下，磁场对II型超导体超导性的破坏可以通过两种方式实现。库珀对可能会因为自旋自由度与场的耦合（泡利顺磁性）或因为场对轨道自由度的影响而破裂。一个新的FFLO相预测发生在附近的Hc 2时，泡利对打破占主导地位的轨道效应。 在这个新的状态下，超导序参量在真实的空间中振荡。有实验证据表明，这种相可能存在于某些重费米子中， 有机超导体对这种全新的超导状态的彻底微观研究将通过NMR技术进行。这种局部技术对于所提出的任务是理想的。美国小组带来了超导材料高场研究的专业知识;格勒诺布尔小组带来了低维系统中磁场感应现象研究的专业知识。此外，格勒诺布尔高磁场实验室提供了在40 mK的极低温度下，在高达33 T的磁场中进行拟议研究的设施。 这项合作为开发这些新量子态的NMR微观研究提供了一个独特的机会。此外，它将允许美国学生在最先进的设施中参加国际研究活动，这些设施与传统培训一起将为他们在学术界或工业界的竞争性职业做好准备。该奖项由材料研究部和国际科学与工程办公室共同资助。

This is a collaborative research effort between the Grenoble High Magnetic Field Laboratory (GHMFL) and Brown University. The general theme of this research is the microscopic study of inhomogeneous superconductivity, i.e., the Fulde-Ferrell-Larkin-Ovchinikov (FFLO) state. The study of this phenomenon is relevant not only to condensed matter physics but to elementary-particle and atomic physics as well. At low temperatures, the destruction of superconductivity by a magnetic field in a type-II superconductor can be accomplished in two ways. Cooper pairs may break up either because of the coupling of the spin degrees of freedom to the field (Pauli paramagnetism) or because of the effect of the field on the orbital degree of freedom. A novel FFLO phase is predicted to occur in the vicinity of Hc2 when Pauli pair breaking dominates over the orbital effects. In this new state the superconducting order parameter oscillates in real space. There is experimental evidence that this phase possibly exists in certain heavy-fermion and organic superconductors. A thorough microscopic study of this fundamentally new superconducting state is to be undertaken through the NMR technique. This local technique is ideal for the proposed task. The U.S. group brings expertise in high field studies of superconducting materials; the Grenoble group brings expertise in the study of magnetic field-induced phenomena in low dimensional systems. In addition, the Grenoble High Magnetic Field Laboratory offers facilities for the proposed studies at very low temperatures, 40 mK, in magnetic fields up to 33 T. The collaboration offers a unique opportunity for developing the NMR microscopic studies of these new quantum states. In addition, it will allow US students to participate in international research activities at state-of-the-art facilities that together with traditional training will prepare them for competitive careers in academia or industry. This award is co-funded by the Division of Materials Research and the Office of International Science and Engineering.