Momentum Dependence of Superconducting Gap, Strong-Coupling Dispersion Kink, And Tightly Bound Cooper Pairs in the High-T(C)(Sr,Ba)(1-X)(K,Na)(X)Fe(2) As(2) Superconductors

We present a systematic angle-resolved photoemission spectroscopic study of the high-T{sub c} superconductor class (Sr/Ba){sub 1-x}K{sub x}Fe{sub 2}As{sub 2}. By utilizing a photon-energy-modulation contrast and scattering geometry we report the Fermi surface and the momentum dependence of the super...

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Bibliographic Details
Published in:Physical review. B, Condensed matter and materials physics Condensed matter and materials physics, 2009-05, Vol.78 (18)
Main Authors: Wray, L., Qian, D., Hsieh, D., Xia, Y., Li, L., Checkelsky, J.G., Pasupathy, A., Gomes, K.K., Parker, C.V., Fedorov, A.V., Chen, G.F., Luo, J.L., Yazdani, A., Ong, N.P., Wang, N.L., Hasan, M.Z.
Format: Article
Language:English
Subjects:
BINDING ENERGY
BRILLOUIN ZONES
COHERENCE LENGTH
CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY
COOPER PAIRS
DISPERSIONS
FERMI LEVEL
GEOMETRY
HIGH-TC SUPERCONDUCTORS
ORDER PARAMETERS
Other,OTHER, PHYS
PHASE SHIFT
PHONONS
PHOTOEMISSION
PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
POTENTIALS
RANGE
SCATTERING
SPIN
SUPERCONDUCTORS
WAVE FUNCTIONS
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Summary:We present a systematic angle-resolved photoemission spectroscopic study of the high-T{sub c} superconductor class (Sr/Ba){sub 1-x}K{sub x}Fe{sub 2}As{sub 2}. By utilizing a photon-energy-modulation contrast and scattering geometry we report the Fermi surface and the momentum dependence of the superconducting gap, {triangle}(k{open_square}). A prominent quasiparticle dispersion kink reflecting strong scattering processes is observed in a binding-energy range of 25--55 meV in the superconducting state, and the coherence length or the extent of the Cooper pair wave function is found to be about 20 {angstrom}, which is uncharacteristic of a superconducting phase realized by the BCS-phonon-retardation mechanism. The observed 40{+-}15 meV kink likely reflects contributions from the frustrated spin excitations in a J{sub 1}-J{sub 2} magnetic background and scattering from the soft phonons. Results taken collectively provide direct clues to the nature of the pairing potential including an internal phase-shift factor in the superconducting order parameter which leads to a Brillouin zone node in a strong-coupling setting.
ISSN:1098-0121
1550-235X