title: Observation of spin susceptibility enhancement in the possible Fulde-Ferrell-Larkin-Ovchinnikov state of CeCoIn(5).
abstract: We report (115)In nuclear magnetic resonance measurements of the heavy-fermion superconductor CeCoIn(5) in the vicinity of the superconducting critical field H(c2) for a magnetic field applied perpendicular to the ĉ axis. A possible inhomogeneous superconducting state, the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state, is stabilized in this part of the phase diagram. In an 11 T applied magnetic field, we observe clear signatures of the two phase transitions: the higher temperature one to the homogeneous superconducting state and the lower temperature phase transition to a FFLO state. We find that the spin susceptibility in the putative FFLO state is significantly enhanced as compared to the value in a homogeneous superconducting state. The implications of this finding for the nature of the low temperature phase are discussed.
authors.affiliation: Department of Physics, Brown University, Providence, Rhode Island 02912, USA.
authors.forename: V F
authors.initials: VF
authors.lastname: Mitrović
authors.forename: M
authors.initials: M
authors.lastname: Horvatić
authors.forename: C
authors.initials: C
authors.lastname: Berthier
authors.forename: G
authors.initials: G
authors.lastname: Knebel
authors.forename: G
authors.initials: G
authors.lastname: Lapertot
authors.forename: J
authors.initials: J
authors.lastname: Flouquet