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arXiv · 0909.0744

Local measurement of the penetration depth in the pnictide superconductor Ba(Fe$_{0.95}$Co$_{0.05}$)$_2$As$_2$

Lan Luan·Ophir M. Auslaender·Thomas M. Lippman·Clifford W. Hicks·Beena Kalisky·Jiun-Haw Chu·James G. Analytis·Ian R. Fisher·John R. Kirtley·Kathryn A. Moler
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Abstract

We use magnetic force microscopy (MFM) and scanning SQUID susceptometry to measure the local superfluid density $ρ_{s}$ in Ba(Fe$_{0.95}$Co$_{0.05}$)$_2$As$_2$ single crystals from 0.4 K to the critical temperature $T_c=18.5$ K. We observe that the penetration depth $λ$ varies about ten times more slowly with temperature than previously published, with a dependence that can be 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 despite the highly disordered vortex pinning.

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Lan Luan, Ophir M. Auslaender, Thomas M. Lippman, Clifford W. Hicks, Beena Kalisky, Jiun-Haw Chu, James G. Analytis, Ian R. Fisher, John R. Kirtley, Kathryn A. Moler. 2010-01-13. Local measurement of the penetration depth in the pnictide superconductor Ba(Fe$_{0.95}$Co$_{0.05}$)$_2$As$_2$. https://doi.org/10.1103/physrevb.81.100501

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