title: Microscopic Study of the Fulde-Ferrell-Larkin-Ovchinnikov State in an All-Organic Superconductor.
abstract: Quasi-two-dimensional superconductors with a sufficiently weak interlayer coupling allow magnetic flux to penetrate in the form of Josephson vortices for in-plane applied magnetic fields. A consequence is the dominance of the Zeeman interaction over orbital effects. In the clean limit, the normal state is favored over superconductivity for fields greater than the paramagnetic limiting field, unless an intermediate, inhomogeneous state is stabilized. Presented here are nuclear magnetic resonance (NMR) studies of the inhomogeneous Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state for β''-(ET)2SF5CH2CF2SO3. The uniform superconductivity-FFLO transition is identified at an applied field value of 9.3(0.1) T at low temperature (T=130  mK), and evidence for a possible second transition between inhomogeneous states at ∼11  T is presented. The spin polarization distribution inferred from the NMR absorption spectrum compares favorably to a single-Q modulation of the superconducting order parameter.
authors.affiliation: Department of Physics and Astronomy, UCLA, Los Angeles, California 90095, USA.
authors.forename: G
authors.initials: G
authors.lastname: Koutroulakis
authors.affiliation: Hochfeld-Magnetlabor Dresden (HLD-EMFL), Helmholtz-Zentrum Dresden-Rossendorf, D-01314 Dresden, Germany.
authors.forename: H
authors.initials: H
authors.lastname: Kühne
authors.affiliation: Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA.|Division of Materials Research, National Science Foundation, Arlington, Virginia 22230, USA.
authors.forename: J A
authors.initials: JA
authors.lastname: Schlueter
authors.affiliation: Hochfeld-Magnetlabor Dresden (HLD-EMFL), Helmholtz-Zentrum Dresden-Rossendorf, D-01314 Dresden, Germany.|Institut für Festkörperphysik, TU Dresden, D-01069 Dresden, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Wosnitza
authors.affiliation: Department of Physics and Astronomy, UCLA, Los Angeles, California 90095, USA.
authors.forename: S E
authors.initials: SE
authors.lastname: Brown