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

Journal Article · Thu May 28 00:00:00 EDT 2009 · Phys. Rev. B78:184508,2008

OSTI ID:953508

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

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.

• Research Organization: SLAC National Accelerator Lab., Menlo Park, CA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC02-76SF00515
• OSTI ID: 953508
• Report Number(s): SLAC-REPRINT-2009-375; TRN: US1000843
• Journal Information: Phys. Rev. B78:184508,2008, Vol. 78, Issue 18; ISSN 1098-0121
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
BINDING ENERGY
BRILLOUIN ZONES
COHERENCE LENGTH
COOPER PAIRS
DISPERSIONS
FERMI LEVEL
GEOMETRY
HIGH-TC SUPERCONDUCTORS
ORDER PARAMETERS
PHASE SHIFT
PHONONS
PHOTOEMISSION
POTENTIALS
RANGE
SCATTERING
SPIN
SUPERCONDUCTORS
WAVE FUNCTIONS
Other
OTHER
PHYS