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arXiv · 0704.0529

Scanning Tunneling Spectroscopy in the Superconducting State and Vortex Cores of the beta-pyrochlore KOs2O6

C. Dubois·G. Santi·I. Cuttat·C. Berthod·N. Jenkins·A. P. Petrović·A. A. Manuel·Ø. Fischer·S. M. Kazakov·Z. Bukowski·J. Karpinski
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Abstract

We performed the first scanning tunneling spectroscopy measurements on the pyrochlore superconductor KOs2O6 (Tc = 9.6 K) in both zero magnetic field and the vortex state at several temperatures above 1.95 K. This material presents atomically flat surfaces, yielding spatially homogeneous spectra which reveal fully-gapped superconductivity with a gap anisotropy of 30%. Measurements performed at fields of 2 and 6 T display a hexagonal Abrikosov flux line lattice. From the shape of the vortex cores, we extract a coherence length of 31-40 Å, in agreement with the value derived from the upper critical field Hc2. We observe a reduction in size of the vortex cores (and hence the coherence length) with increasing field which is consistent with the unexpectedly high and unsaturated upper critical field reported.

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C. Dubois, G. Santi, I. Cuttat, C. Berthod, N. Jenkins, A. P. Petrović, A. A. Manuel, Ø. Fischer, S. M. Kazakov, Z. Bukowski, J. Karpinski. 2007-04-04. Scanning Tunneling Spectroscopy in the Superconducting State and Vortex Cores of the beta-pyrochlore KOs2O6. https://doi.org/10.1103/physrevlett.101.057004

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