6 research outputs found
Depairing currents in superconducting films of Nb and amorphous MoGe
We report on measuring the depairing current J_{dp} in thin superconducting
films as a function of temperature. The main difficulties in such measurements
are that heating has to be avoided, either due to contacts, or to vortex flow.
The latter is almost unavoidable since the sample cross-section is usually
larger than the superconducting coherence length \xi_s and the magnetic field
penetration depth \lambda_s. On the other hand, vortex flow is helpful since it
homogenizes the distribution of the current across the sample. We used a pulsed
current method, which allows to overcome the difficulties caused by dissipation
and measured the depairing current in films of thin polycrystalline Nb (low
\lambda_s, low specific resistance \rho) and amorphous Mo_{0.7}Ge_{0.3} (high
\lambda_s, high \rho), structured in the shape of bridges of various width. The
experimental values of J_{dp} for different bridge dimensions are compared with
theoretical predictions by Kupriyanov and Lukichev for dirty limit
superconductors. For the smallest samples we find a very good agreement with
theory, over essentially the whole temperature interval below the
superconducting critical temperature.Comment: 5 pages, 6 figure