Absolute value and temperature dependence of the magnetic penetration depth in Ba(Co0.074Fe0.926)(2)As-2
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The absolute value and temperature dependence of the in-plane magnetic penetration depth λ have been measured on a single crystal of Ba(Co0.074Fe0.926)2As2 using low-energy muon-spin rotation and microwave cavity perturbation. The magnetic field profiles in the Meissner state are consistent with a local London model beyond a depth of 15 nm. We determine the gap symmetry through measurements of the temperature dependence of the superfluid density which follows a two-gap s-wave model over the entire temperature range below Tc. While the intermediate to high temperature data is well fit by an energy gap model in the BCS-like (weak-coupling) limit, a second smaller gap becomes apparent at low temperatures.
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This article is published as Ofer, Oren, J. C. Baglo, M. D. Hossain, R. F. Kiefl, W. N. Hardy, A. Thaler, H. Kim et al. "Absolute value and temperature dependence of the magnetic penetration depth in Ba (Co 0.074 Fe 0.926) 2 As 2." Physical Review B 85, no. 6 (2012): 060506. DOI: 10.1103/PhysRevB.85.060506. Posted with permission.