Browsing by Author "Hu, J.P."

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    Observation of Momentum-Confined In-Gap Impurity State in Ba0.6K0.4Fe2As2: Evidence for Antiphase s± Pairing
    (American Physical Society, 2014) Zhang, P.; Richard, P.; Qian, T.; Shi, X.; Ma, J.; Zeng, L.-K.; Wang, X.-P.; Rienks, E.; Zhang, C.-L.; Dai, Pengcheng; You, Y.-Z.; Weng, Z.-Y.; Wu, X.-X.; Hu, J.P.; Ding, H.
    We report the observation by angle-resolved photoemission spectroscopy of an impurity state located inside the superconducting gap of Ba 0.6 K 0.4 Fe 2 As 2 and vanishing above the superconducting critical temperature, for which the spectral weight is confined in momentum space near the Fermi wave-vector positions. We demonstrate, supported by theoretical simulations, that this in-gap state originates from weak scattering between bands with opposite sign of the superconducting-gap phase. This weak scattering, likely due to off-plane nonmagnetic (Ba, K) disorder, occurs mostly among neighboring Fermi surfaces, suggesting that the superconducting-gap phase changes sign within holelike (and electronlike) bands. Our results impose severe restrictions on the models promoted to explain high-temperature superconductivity in these materials.