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.