Scanning tunneling spectroscopy in the superconducting state and vortex cores of the beta-pyrochlore KOs2O6.
We performed the first scanning tunneling spectroscopy measurements on the pyrochlore superconductor KOs2O6 (T(c)=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 A, in agreement with the value derived from the upper critical field H(c2). 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.
Dubois
C
C
DPMC-MaNEP, Université de Genève, Quai Ernest-Ansermet 24, Genève 4, Switzerland. duboisc@mit.edu
Santi
G
G
Cuttat
I
I
Berthod
C
C
Jenkins
N
N
Petrović
A P
AP
Manuel
A A
AA
Fischer
O
O
Kazakov
S M
SM
Bukowski
Z
Z
Karpinski
J
J