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Title: Doping-evolution of the superconducting gap in single crystals of (Ca 1-x La x ) 10 (Pt 3 As 8 )(Fe 2 As 2 ) 5 superconductor from London penetration depth measurements

The doping-evolution of the superconducting gap structure in iron-based superconductor (Ca1-xLax)10(Pt3As8)(Fe2As2)5(x = 0.04, 0.06, 0.09, 0.11, and 0.18) was probed by high-resolution measurements of the London penetration depth, λ(T). The samples spanned compositions from underdoped to slightly overdoped with superconducting critical temperatures, Tc, from 12.7 K (x = 0.04) through (optimal) 23.3 K (x = 0.11) to 21.9 K (x = 0.18). The low-temperature variation (up to 0.3 Tc ) of λ(T) was analysed using a power-law function, Δλ = ATn. For compositions close to the optimal doping, (x = 0.09, 0.11, and 0.18), characterized by Tc > 20K, Δλ(T) shows a tendency to saturation, indicative of a full gap on the Fermi surface. Fitting over the lowest temperature range (T < 0.1 Tc) gives n = 2.6. This value is well outside the range 1 ≤ n ≤ 2 expected for the line-nodal superconductor. The exponent n decreased to n ~ 2 in the two most underdoped compositions x = 0.04 (Tc = 12.7 K) and 0.06 (Tc = 18.2 K), implying the development of a notable gap anisotropy revealed by the enhanced influence of pair-breaking scattering. This decrease is accompanied by a significant increase of the total variationmore » of the penetration depth Δλ in a fixed temperature interval (e.g., Tmin - 0.3Tc). Both the decrease of the exponent and the increase of the absolute value of Δλ in the underdoped regime are similar to the observations in other charge-doped iron-based superconductors, such as doped BaFe2As2 and NaFeAs, suggesting a universal behavior in iron-based superconductors.« less
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Publication Date:
OSTI Identifier:
Report Number(s):
IS-J 8556
Journal ID: ISSN 0953-2048
DOE Contract Number:
Resource Type:
Journal Article
Resource Relation:
Journal Name: Superconductor Science and Technology; Journal Volume: 27; Journal Issue: 10
IOP Publishing
Research Org:
Ames Laboratory (AMES), Ames, IA (United States)
Sponsoring Org:
Country of Publication:
United States