Muon spin rotation measurement of the magnetic field penetration depth in Ba(Fe0.926Co0.074)2As2: Evidence for multiple superconducting gaps

T. J. Williams; A. A. Aczel; E. Baggio-Saitovitch; S. L. Bud’ko; P. C. Canfield; J. P. Carlo; T. Goko; J. Munevar; N. Ni; Y. J. Uemura; W. Yu; G. M. Luke

doi:10.1103/PhysRevB.80.094501

Muon spin rotation measurement of the magnetic field penetration depth in Ba(Fe0.926Co0.074)2As2: Evidence for multiple superconducting gaps

T. J. Williams, A. A. Aczel, E. Baggio-Saitovitch, S. L. Bud’ko, P. C. Canfield, J. P. Carlo, T. Goko, J. Munevar, N. Ni, Y. J. Uemura, W. Yu, G. M. Luke

DOI 10.1103/PhysRevB.80.094501 · Physical Review B

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Abstract

We have performed transverse field muon spin rotation measurements of single crystals of Ba(Fe0.926Co0.074)2As2 with the applied magnetic field along the ĉ direction. Fourier transforms of the measured spectra reveal an anisotropic line-shape characteristic of an Abrikosov vortex lattice. We have fit the μSR spectra to a microscopic model in terms of the penetration depth λ and the Ginzburg-Landau parameter κ. We find that as a function of temperature, the penetration depth varies more rapidly than in standard weak-coupled BCS theory. For this reason we first fit the temperature dependence to a power law where the power varies from 1.6 to 2.2 as the field changes from 0.02 to 0.1 T. Due to the surprisingly strong field dependence of the power and the superfluid density we proceeded to fit the temperature dependence to a two-gap model, where the size of the two gaps is field independent. From this model, we obtained gaps of 2Δ1=3.77kBTC and 2Δ2=1.57kBTC, corresponding to roughly 6 and 3 meV, respectively.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
Ba(Fe0.926Co0.074)2As2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	22.5	Pressure not reported	midpoint
Ba(Fe0.926Co0.074)2As2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	22.2	Pressure not reported	unknown
Ba(Fe0.926Co0.074)2As2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	22.1	Pressure not reported	unknown
LaFeAsO Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
BaFe2As2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
LaFeAs(O1-xFx) Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	56	Pressure not reported	unknown
(Ba1-xKx)Fe2As2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	38	Pressure not reported	unknown
La(Fe1-xCox)AsO Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	14	Pressure not reported	unknown
Ba(Fe1-xCox)2As2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	23	Pressure not reported	unknown
YBa2Cu3O6.97 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
MgB2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	39	Pressure not reported	unknown