5 research outputs found
Anatomy of point-contact Andreev reflection spectroscopy from the experimental point of view (review)
We review application of point-contact Andreev-reflection spectroscopy to
study elemental superconductors, where theoretical conditions for the smallness
of the point-contact size with respect to the characteristic lengths in the
superconductor can be satisfied. We discuss existing theoretical models and
identify new issues that have to be solved, especially when applying this
method to investigate more complex superconductors. We will also demonstrate
that some aspects of point-contact Andreev-reflection spectroscopy still need
to be addressed even when investigating ordinary metals.Comment: 20 pages, 18 figs. V2: Ref.60 and footnote 3 are added, a number of
minor fixe
Investigation of the superconducting energy gap in the compound LuNiBC by the method of point contact spectroscopy: two-gap approximation
It is shown that the two-gap approximation is applicable for describing the
spectra of LuNiBC-Ag point contacts in a wide interval
of temperatures. The values and the temperature dependences of the large and
the small gaps in the plane and in the direction were estimated using
the generalized BTK model and the equations of Beloborodko. In the BCS
extrapolation the critical temperature of the small gap is 10 in the
plane and 14.5 in the direction. The absolute values of the gaps are
and . For the large gaps the
critical temperature coincides with the bulk , , and
their absolute values are very close, being about 3 in both orientations.
In the direction the contributions to the conductivity from the small and
the large gaps remain practically identical up to . In the
plane the contribution from the small gap is much smaller and decreases rapidly
as a temperature rises.Comment: 10 pages, 10 figures, submitted to Fiz. Nizk. Temp. (Low Temp. Phys.
The Superconducting Gap Behavior in the Antiferromagnetic Nickel-Borocarbide Compounds RNi2B2C (R=Dy, Ho, Er, Tm) Studied by Point-Contacts Spectroscopy
An general survey of the superconducting (SC) gap study in the title
compounds by point-contact (PC) spectroscopy is presented. The SC gap was
determined from dV/dI of PCs employing the well-known theory of conductivity
for normal metal-superconductor PCs accounting Andreev reflection. The theory
was modified by including pair-breaking effects considering the presence of
magnetic rare-earth ions. A possible multiband structure of these compounds was
also taken into account. The PC study of the gap in the Er-compound
(TN=6K<Tc=11K) gives =evidence for the presence of two SC gaps. Additionally, a
distinct decrease of both gaps is revealed for R = Er in the antiferromagnetic
(AF) state. For R = Tm (TN=1.5K<Tc=10.5K) a decrease of the SC gap is observed
below 4-5K, while for R = Dy (TN=10.5K>Tc=6.5K) the SC gap has a BCS-like
dependence in the AF state. The SC gap for R = Ho (TN=5.2K<Tc=8.5K) exhibits
below T*=5.6K a single-band BCS-like dependence vanishing above T*, where a
specific magnetic order occurs. The difference in the SC gap behavior in the
title compounds is attributed to different AF ordering.Comment: 4 pages, 4 figs., submitted to LT25; V2. missed author is adde