Doping-evolution of the superconducting gap in single crystals of (Ca1-xLax)(10)(Pt3As8)(Fe2As2)(5) superconductor from London penetration depth measurements

作者：Cho K^*; Tanatar M A; Ni N; Prozorov R

来源：Superconductor Science and Technology, 2014, 27(10): 104006.

DOI：10.1088/0953-2048/27/10/104006

• London penetration depth
• iron based superconductors
• pairing mechanisms

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, lambda(T). The samples spanned compositions from underdoped to slightly overdoped with superconducting critical temperatures, T-c, 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 T-c) of lambda(T) was analysed using a power-law function, Delta lambda = AT(n). For compositions close to the optimal doping, (x = 0.09, 0.11, and 0.18), characterized by T-c > 20K, Delta lambda(T) shows a tendency to saturation, indicative of a full gap on the Fermi surface. Fitting over the lowest temperature range (T< 0.1T(c)) 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 similar to 2 in the two most underdoped compositions x = 0.04 (T-c = 12.7 K) and 0.06 (T-c = 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 variation of the penetration depth Delta lambda in a fixed temperature interval (e.g., T-min - 0.3 T-c). Both the decrease of the exponent and the increase of the absolute value of Delta lambda 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.

• 出版日期2014-10