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Title: Observation of Momentum-Confined In-Gap Impurity State in Ba 0.6 K 0.4 Fe 2 As 2 : Evidence for Antiphase s ± Pairing

Authors:
; ; ; ; ; ; ; ; ; ; ; ; ; ;
Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
1181589
Grant/Contract Number:
FG02-05ER46202
Resource Type:
Journal Article: Published Article
Journal Name:
Physical Review X
Additional Journal Information:
Journal Volume: 4; Journal Issue: 3; Related Information: CHORUS Timestamp: 2016-12-23 13:42:39; Journal ID: ISSN 2160-3308
Publisher:
American Physical Society
Country of Publication:
United States
Language:
English

Citation Formats

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., and Ding, H.. Observation of Momentum-Confined In-Gap Impurity State in Ba 0.6 K 0.4 Fe 2 As 2 : Evidence for Antiphase s ± Pairing. United States: N. p., 2014. Web. doi:10.1103/PhysRevX.4.031001.
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.. Observation of Momentum-Confined In-Gap Impurity State in Ba 0.6 K 0.4 Fe 2 As 2 : Evidence for Antiphase s ± Pairing. United States. doi:10.1103/PhysRevX.4.031001.
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., and Ding, H.. 2014. "Observation of Momentum-Confined In-Gap Impurity State in Ba 0.6 K 0.4 Fe 2 As 2 : Evidence for Antiphase s ± Pairing". United States. doi:10.1103/PhysRevX.4.031001.
@article{osti_1181589,
title = {Observation of Momentum-Confined In-Gap Impurity State in Ba 0.6 K 0.4 Fe 2 As 2 : Evidence for Antiphase s ± Pairing},
author = {Zhang, P. and Richard, P. and Qian, T. and Shi, X. and Ma, J. and Zeng, L. -K. and Wang, X. -P. and Rienks, E. and Zhang, C. -L. and Dai, Pengcheng and You, Y. -Z. and Weng, Z. -Y. and Wu, X. -X. and Hu, J. P. and Ding, H.},
abstractNote = {},
doi = {10.1103/PhysRevX.4.031001},
journal = {Physical Review X},
number = 3,
volume = 4,
place = {United States},
year = 2014,
month = 7
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1103/PhysRevX.4.031001

Citation Metrics:
Cited by: 11works
Citation information provided by
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  • We present detailed measurements of the temperature-dependent Raman spectra of optimally doped Ba 0.6K 0.4Fe 2As 2 and analyze the low-temperature spectra based on local-density-approximation band-structure calculations and the subsequent estimation of effective Raman vertices. Experimentally, a narrow, emergent mode appears in the B 1g (d x2-y2) Raman spectra only below T c, well into the superconducting state and at an energy below twice the energy gap on the electron Fermi-surface sheets. The Raman spectra can be reproduced quantitatively with estimates for the magnitude and momentum-space structure of an A 1g (s-wave) pairing gap on different Fermi-surface sheets, as wellmore » as the identification of the emergent sharp feature as a Bardasis-Schrieffer exciton. Formed as a Cooper-pair bound state in a subdominant d x2-y2 channel, the binding energy of the exciton relative to the gap edge shows that the coupling strength in the subdominant channel is as strong as 60% of that in the dominant s-wave channel. This result suggests that d x2-y2 may be the dominant pairing symmetry in Fe-based superconductors that lack central hole bands.« less
  • Cited by 66
  • We report comprehensive 77 Se NMR measurements on a single crystalline sample of the recently discovered FeSe-based high-temperature superconductor K x Fe 2 - y Se 2 ( T c = 33 K) in a broad temperature range up to 290 K. Despite deviations from the stoichiometric KFe 2 Se 2 composition, we observed 77 Se NMR line shapes as narrow as 4.5 kHz under a magnetic field applied along the crystal c axis, and found no evidence for co-existence of magnetic order with superconductivity. On the other hand, the 77 Se NMR line shape splits into two peaks withmore » equal intensities at all temperatures when we apply the magnetic field along the ab plane. This suggests that K vacancies may have a superstructure and that the local symmetry of the Se sites is lower than the tetragonal fourfold symmetry of the average structure. This effect might be a prerequisite for stabilizing the s ± symmetry of superconductivity in the absence of the hole bands at the Brillouin zone center. From the increase of NMR linewidth below T c induced by the Abrikosov lattice of superconducting vortices, we estimate the in-plane penetration depth λ ab ~ 290 nm and the carrier concentration n e ~ 1 × 10 + 21 cm - 3 . Our Knight shift 77 K data indicate that the uniform spin susceptibility decreases progressively with temperature, in analogy with the case of FeSe ( T c ~ 9 K) as well as other FeAs high- T c systems. The strong suppression of 77 K observed immediately below T c for all crystal orientations is consistent with a singlet pairing of Cooper pairs. We do not however observe the Hebel-Slichter coherence peak of the nuclear spin-lattice relaxation rate 1 / T 1 immediately below T c , expected for conventional BCS s-wave superconductors. In contrast with the case of FeSe, we do not observe evidence for an enhancement of low-frequency antiferromagnetic spin fluctuations near T c in 1 / T 1 T . Instead, 1 / T 1 T exhibits qualitatively the same behavior as overdoped non-superconducting Ba(Fe 1 - x Co x ) 2 As 2 with x ~ 0 . 14 or greater, where hole bands are missing in the Brillouin zone center. We will discuss the implications of our results on the unknown mechanism of high-temperature superconductivity in FeSe and FeAs systems.« less
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