227 research outputs found

    Determination of the pairing state in iron-based superconductors through neutron scattering

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    We calculate the spin susceptibility in the s_{+-} and s_{++} superconducting states of the iron pnictides using the effective five orbital model and considering the quasiparticle damping. For the experimentally evaluated magnitude of the quasiparticle damping and the superconducting gap, the results at the wave vector ~ (pi,0) show that the s_{+-} state is more consistent with the neutron scattering experiments, while for larger quasiparticle damping and the superconducting gap, the s_{++} state can be more consistent. To distinguish between two cases that reproduce the experiments at the wave vector ~ (pi,0), we propose to investigate experimentally the wave vector ~ (pi,pi).Comment: 5pages, 3 figures, Accepted in Phys. Rev.

    Hidden robust presence of a hole Fermi surface in a heavily electron doped iron based superconductor LaFe2_2As2_2

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    We investigate the electronic structure of a recently discovered, heavily electron-doped iron based superconductor LaFe2_2As2_2. Although first principles calculation shows apparent absence of hole Fermi surfaces around the Ξ“\Gamma point, we reveal, by hypothetically removing the La dd orbital contribution, that a hole Fermi surface around the Ξ“\Gamma point is essentially present. In the collapsed phase of LaFe2_2As2_2, which is non-superconducting, the hole Fermi surface is found to be absent, and the difference from the uncollapsed superconducting phase can be naturally understood within the spin-fluctuation mediated pairing scenario.Comment: 6 pages, 4 figure
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