Abstract
The absolute value and temperature dependence of the in-plane magnetic penetration depth have been measured on a single crystal of Ba(CoFeAs 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 -wave model over the entire temperature range below . 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.
- Received 6 February 2012
DOI:https://doi.org/10.1103/PhysRevB.85.060506
©2012 American Physical Society