Publication: Scanning Tunneling Spectroscopy and Vortex Imaging in the Iron Pnictide Superconductor BaFe1:8Co0:2As2
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Date
2009
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American Physical Society
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Yin, Yi, Martin Zech, Tess L. Williams, W. F. Wang, G. Wu, X. H. Chen, and Jennifer E. Hoffman. 2009. Physical Review Letters 102(9): 097002.
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Abstract
We present an atomic resolution scanning tunneling spectroscopy study of superconducting
BaFe<sub>1.8</sub>Co<sub>0.2</sub>As<sub>2</sub> single crystals in magnetic fields up to 9 T. At zero field, a single gap with coherence
peaks at [untranscribable character] = 6:25 meV is observed in the density of states. At 9 and 6 T, we image a disordered vortex
lattice, consistent with isotropic, single flux quantum vortices. Vortex locations are uncorrelated with
strong-scattering surface impurities, demonstrating bulk pinning. The vortex-induced subgap density of
states fits an exponential decay from the vortex center, from which we extract a coherence length [untranscribable character] =
27:6 +/- 2:9 [untranscribable character], corresponding to an upper critical field H<sub>c</sub>2 = 43 T.
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