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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)_xFe_2As_2 superconductors

Wray, L. and Qian, D. and Hsieh, D. and Xia, Y. and Li, L. and Checkelsky, J. G. and Pasupathy, A. and Gomes, K. K. and Parker, C. V. and Fedorov, A. V. and Chen, G. F. and Luo, J. L. and Yazdani, A. and Ong, N. P. and Wang, N. L. and Hasan, M. Z. (2008) 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)_xFe_2As_2 superconductors. Physical Review B, 78 (18). Art. No. 184508. ISSN 1098-0121. http://resolver.caltech.edu/CaltechAUTHORS:20140908-100342412

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Abstract

We present a systematic angle-resolved photoemission spectroscopic study of the high-Tc superconductor class (Sr/Ba)_(1−x)K_xFe_2As_2. By utilizing a photon-energy-modulation contrast and scattering geometry we report the Fermi surface and the momentum dependence of the superconducting gap, Δ(k⃗ ). 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 Å, 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_1-J_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.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1103/PhysRevB.78.184508DOIArticle
http://journals.aps.org/prb/abstract/10.1103/PhysRevB.78.184508PublisherArticle
ORCID:
AuthorORCID
Hsieh, D.0000-0002-0812-955X
Alternate Title:Momentum dependence of superconducting gap, strong-coupling dispersion kink, and tightly bound Cooper pairs in the high-Tc (Sr,Ba)1−x(K,Na)xFe2As2 superconductors
Additional Information:© 2008 The American Physical Society. Received 12 September 2008. Revised 29 September 2008. Published 10 November 2008. We acknowledge discussions with D. A. Huse, P. W. Anderson, S. Sachdev, D.-H. Lee, and B. A. Bernevig. This work is supported by DOE Grant No. DEFG-02–05ER46200 and NSF Grant No. DMR-0213706. The use of ALS at LBNL and SSRL at SLAC are supported by the U.S. DOE.
Funders:
Funding AgencyGrant Number
Department of Energy (DOE)DEFG-02–05ER46200
Department of Energy (DOE)DMR-0213706
Issue or Number:18
Classification Code:PACS numbers: 74.20.Mn, 74.25.Jb, 74.70.b, 74.72.h
Record Number:CaltechAUTHORS:20140908-100342412
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20140908-100342412
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:49329
Collection:CaltechAUTHORS
Deposited By: Joy Painter
Deposited On:08 Sep 2014 17:22
Last Modified:22 Aug 2019 22:41

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