Article (Scientific journals)
Lower critical field and SNS-Andreev spectroscopy of 122-arsenides: Evidence of nodeless superconducting gap
Abdel-Hafiez, M.; Pereira, P.J.; Kuzmichev, S.A. et al.
2014In Physical Review. B, Condensed Matter, 90, p. 054524
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Keywords :
FeAs Superconductors; Arsenides
Abstract :
[en] Using two experimental techniques, we studied single crystals of the 122-FeAs family with almost the same critical temperature, Tc. We investigated the temperature dependence of the lower critical field Hc1(T) of a Ca0.32Na0.68Fe2As2 (Tc ≈ 34 K) single crystal under static magnetic fields H parallel to the c axis. The temperature dependence of the London penetration depth can be described equally well either by a single anisotropic s-wave-like gap or by a two-gap model, while a d-wave approach cannot be used to fit the London penetration depth data. Intrinsic multiple Andreev reflection effect spectroscopy was used to detect bulk gap values in single crystals of the intimate compound Ba0.65K0.35Fe2As2, with the same Tc. We estimated the range of the large gap value L = 6–8 meV (depending on small variation of Tc) and its a k space anisotropy of about 30%, and the small gap Delta ≈ 1.7 ± 0.3 meV. This clearly indicates that the gap structure of our investigated systems more likely corresponds to a nodeless s-wave two gaps.
Disciplines :
Physics
Author, co-author :
Abdel-Hafiez, M.;  Université de Liège - ULiège
Pereira, P.J.;  Katholieke Universiteit Leuven - KUL
Kuzmichev, S.A.;  Lomonosov Moscow State University - MSU
Kuzmicheva, T.E.;  Lebedev Physical Institute
Pudalov, V.M.;  Lebedev Physical Institute
Harnagea, L.;  Leibniz Institute for Solid State and Materials Research, IFW-Dresden, D-01171 Dresden, Germany
Kordyuk, A.A.;  Institute of Metal Physics of National Academy of Sciences of Ukraine, 03142 Kyiv, Ukraine
Silhanek, Alejandro  ;  Université de Liège - ULiège > Département de physique > Physique expérimentale des matériaux nanostructurés
Moshchalkov, V.V.;  Katholieke Universiteit Leuven - KUL
Shen, B.;  Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
Wen, Hai-Hu;  National Laboratory for Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, China
Vasiliev, A.N.;  Lomonosov Moscow State University - MSU
Chen, Xiao-Jia;  Center for High Pressure Science and Technology Advanced Research, 1690 Cailun Road, Shanghai 201203, China
More authors (3 more) Less
Language :
English
Title :
Lower critical field and SNS-Andreev spectroscopy of 122-arsenides: Evidence of nodeless superconducting gap
Publication date :
29 August 2014
Journal title :
Physical Review. B, Condensed Matter
ISSN :
0163-1829
eISSN :
1095-3795
Publisher :
American Institute of Physics, New York, United States - New York
Volume :
90
Pages :
054524
Peer reviewed :
Peer Reviewed verified by ORBi
Funders :
ULg - Université de Liège [BE]
Funding text :
Crédit de Démarrage ULg
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