title: Fulde-Ferrell-Larkin-Ovchinnikov state in a perpendicular field of quasi-two-dimensional CeCoIn5.
abstract: A Fulde-Ferrell-Larkin-Ovchinnkov (FFLO) state was previously reported in the quasi-2D heavy fermion CeCoIn5 when a magnetic field was applied parallel to the ab plane. Here, we conduct 115In NMR studies of this material in a perpendicular field, and provide strong evidence for FFLO in this case as well. Although the topology of the phase transition lines in the H-T phase diagram is identical for both configurations, there are several remarkable differences between them. Compared to H parallelab, the FFLO phase for H perpendicularab is confined in a much narrower region at the low-T-high-H corner in the H-T plane, and the critical field separating the FFLO and non-FFLO superconducting states almost ceases to have a temperature dependence. Moreover, directing H perpendicularab results in a notable change in the quasiparticle excitation spectrum within the planar node associated with the FFLO transition.
authors.affiliation: Division of Physics, Graduate School of Science, Hokkaido University, Sapporo 060-0810, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Kumagai
authors.forename: M
authors.initials: M
authors.lastname: Saitoh
authors.forename: T
authors.initials: T
authors.lastname: Oyaizu
authors.forename: Y
authors.initials: Y
authors.lastname: Furukawa
authors.forename: S
authors.initials: S
authors.lastname: Takashima
authors.forename: M
authors.initials: M
authors.lastname: Nohara
authors.forename: H
authors.initials: H
authors.lastname: Takagi
authors.forename: Y
authors.initials: Y
authors.lastname: Matsuda