Pinnning and critical currents of heterogeneous superconductors in various structural states
V.I. Sokolenko1 and V.I. Karas`1,2
1National Science Center “Kharkov Institute of Physics and Technology” 1 Akademicheskaya Str., Kharkov 61108, Ukrain
2V. Karazin Kharkov National University, 4 Svobody Sq., Kharkov 61107, Ukraine
Received October 10, 2017
An increase in the critical currents of a composite Nb3Sn-based superconductor as a result of a low-intensity ultrasound action is shown. In the framework of the mechanism of vortex interaction with a grain boundary based on scattering of electrons at the boundary, the decrease in the compressive stresses in the Nb3Sn layer when ultrasonic is action leads to an increase in the elementary pinning force due to decrease the coherence length, and increase in both the superconducting transition temperature, and the electronic heat capacity coefficient. It is shown that for single-crystal niobium with a high density of uniformly distributed dislocations in fields close to Hc2, the field dependence of the pinning volume force corresponds to a system of effective point centers satisfying the criterion of sparse. The first-order interaction of a vortex with such pinning centers is much larger than the characteristic of the interaction of a vortex with a single helical and edge dislocation.
PACS: 62.30.+d Mechanical and elastic waves; vibrations;
Key words: ultrasound action, composite superconductor, pinning force, critical currents.
Published online: January 25, 2018