Abstract
The London penetration depth was measured in optimally doped BaKFeAs crystals, with and without columnar defects produced by 1.4 GeV Pb irradiation. The low temperature behavior of unirradiated samples was consistent with a fully gapped superconducting state with a minimum energy gap . Similar gap values were observed for irradiation levels corresponding to mean column-column separations of 32 and 22 nm. At very high irradiation levels (column-column separation of 10 nm) a power law was observed below , most likely due to elevated scattering. Neither the location nor the sharpness of the superconducting transition was affected by irradiation. The data provide evidence for an pairing state.
- Received 28 February 2013
DOI:https://doi.org/10.1103/PhysRevB.87.180502
©2013 American Physical Society