Superconductivity of LaFe1-yCoyAsO1-xFx

Flux growth at ambient pressure of millimeter-sized single crystals of LaFeAsO, LaFeAsO1−xFx, and LaFe1−xCoxAsO

Millimeter-sized single crystals of LaFeAsO, LaFeAsO1−xFx, and LaFe1−xCoxAsO were grown in NaAs flux at ambient pressure. The detailed growth procedure and crystal characterizations are reported. The as-grown crystals have typical dimensions of3×4×0.05–0.3 mm3 with the crystallographic c-axis perpendicular to the plane of the platelike single crystals. Various characterizations confirmed the hi...

Unconventional superconductivity with a sign reversal in the order parameter of LaFeAsO1-xFx.

We argue that the newly discovered superconductivity in a nearly magnetic, Fe-based layered compound is unconventional and mediated by antiferromagnetic spin fluctuations, though different from the usual superexchange and specific to this compound. This resulting state is an example of extended s-wave pairing with a sign reversal of the order parameter between different Fermi surface sheets. Th...

Magnetism in CeFeAsO1−xFx and LaFeAsO1−xFx from first principles

S. Sharma,1,2,3,* S. Shallcross,4 J. K. Dewhurst,1,2,3 A. Sanna,2,5 C. Bersier,1,2,3 S. Massidda,5 and E. K. U. Gross2,3 1Fritz Haber Institute of the Max Planck Society, Faradayweg 4-6, D-14195 Berlin, Germany 2Institut für Theoretische Physik, Freie Universität Berlin, Arnimallee 14, D-14195 Berlin, Germany 3European Theoretical Spectroscopy Facility (ETSF) 4Lehrstuhl für Theoretische Festkör...

Magnetic Order versus Superconductivity in the Iron - based La ( O 1 - xFx ) FeAs Systems

Coexistence of magnetic fluctuations and superconductivity in the pnictide high temperature superconductor SmFeAsO1-xFx measured by muon spin rotation.

Muon spin rotation experiments were performed on the pnictide high temperature superconductor SmFeAsO1-xFx with x=0.18 and 0.3. We observed an unusual enhancement of slow spin fluctuations in the vicinity of the superconducting transition which suggests that the spin fluctuations contribute to the formation of an unconventional superconducting state. An estimate of the in-plane penetration dept...