07. Local measurement of the penetration depth in the pnictide superconductor Ba(Fe0.95Co0.05)2As2

Lan Luan, O.M Auslaender, T. M. Lippman, C. W. Hicks, B. Kalisky, J. Chu, J. G. Analytis, I. R. Fisher, J. R. Kirtley and K. A. Moler

Physical Review B, 81, 100501(R) (2010)

We use magnetic force microscopy (MFM) to measure the local penetration depth λ in Ba ( Fe 0.95 Co 0.05 ) 2 As 2 single crystals and use scanning superconducting quantum interference device susceptometry to measure its temperature variation down to 0.4 K. We observe that superfluid density ρ s over the full temperature range is well described by a clean two-band fully gapped model. We demonstrate that MFM can measure the important and hard-to-determine absolute value of λ , as well as obtain its temperature dependence and spatial homogeneity. We find ρ s to be uniform on the submicron scale despite the highly disordered vortex pinning.