36 research outputs found
Experimental study of intrinsic multiple Andreev reflections effect in GdO(F)FeAs superconductor array junctions
We report the first observation of the intrinsic multiple Andreev reflections
effect (IMARE) in S-n-S-...-S-arrays (S = superconductor, n = normal metal)
formed by "break-junction" technique in GdO(F)FeAs superconductor (Tc = 48 - 53
K). We show that superconducting gap peculiarities at dI/dV-spectra sharpen
dramatically in the arrays as compared with that in the single-contact spectra;
this enables to improve significantly accuracy of the bulk superconducting
parameters determination. Using IMARE, we determined the large and the small
gap values \Delta_L = 11 +- 1.1 meV and \Delta_S = 2.6 +- 0.4 meV. The
BCS-ratio 2\Delta_L/kTc^{local} = 5.0 - 5.9 > 3.52 (Tc^{local} is the contact
area critical temperature) evidences for a strong electron-boson coupling. The
results obtained agree well with our previous data by Andreev spectroscopy for
single SnS-contacts.Comment: 6 pages, 6 figure
Observation of Multi-Gap Superconductivity in GdO(F)FeAs by Andreev Spectroscopy
We have studied current-voltage characteristics of Andreev contacts in
polycrystalline GdOFFeAs samples with bulk critical
temperature = (52.5 \pm 1)K using break-junction technique. The data
obtained cannot be described within the single-gap approach and suggests the
existence of a multi-gap superconductivity in this compound. The large and
small superconducting gap values estimated at T = 4.2K are {\Delta}L = 10.5 \pm
2 meV and {\Delta}S = 2.3 \pm 0.4 meV, respectively.Comment: 5 pages, 4 figures, submitted to JETP Letter
Study of the Two-Gap Superconductivity in GdO(F)FeAs by ScS-Andreev Spectroscopy
Current-voltage characteristics and dynamic conductance of the superconductor
- constriction - superconductor junctions in GdO(F)FeAs polycrystalline samples
with critical temperatures Tc^local = 46 - 53 K were investigated. Two
superconducting gaps, the large Delta_L = 10.5 +- 2 meV, and the small one
Delta_S = 2.3 +- 0.4 meV were clearly observed at T = 4.2 K. The
2Delta_L/kTc^local = 5.5 +- 1 ratio gives support to the strong coupling
mechanism which is responsible for the high Tc value. Temperature dependence of
the large gap Delta_L(T) indicates the presence of intrinsic proximity effect
(in k-space) between two superconducting condensates.Comment: 7 pages, 6 figures. Submitted to Journal of Physics: Conference
Serie