Normal-superconducting transition induced by high current densities inYBa2Cu3O

Abstract

Current-voltage characteristics of top-seeded melt-textured YBa 2 Cu 3 O 7Ϫ␦ are presented. The samples were cut out of centimetric monoliths. Films characteristics were also measured on microbridges patterned on thin films grown by dc sputtering. For both types of samples, a quasidiscontinuity or quenching was observed for a current density J* several times the critical current density J c . Though films and bulks differ much in their magnitude of both J c and J*, a proposal is made as to a common intrinsic origin of the quenching phenomenon. The unique temperature dependence observed for the ratio J*/J c , as well as the explanation of the prequenching regime in terms of a single dissipation model, lends support to our proposal.

Pinning effects on self-heating and flux-flow instability in superconducting films near Tc

“…Following the BS approach we note that the quasiparticles temperature in Eq. ( 9) is independent of the electric field E. It should be found from the heat balance equation (5), which in the presence of pinning reads…”

“…In general, various mechanisms were suggested to explain voltage jumps in the CVCs of superconductors. To name a few, these are a thermal runaway effect due to Joule heating [4,5], formation of localized normal domains which appear in places of maximum current due to an inhomogeneous current distribution [6,7], crystallization of the vortex system [8,9], phase-slip centers or lines [10,11], and the Kunchur hot-electron instability [12,13] observed at T 0.5T c and related to thermal effects diminishing the superconducting order parameter, thus leading to an expansion of the vortex cores.…”

Flux Exclusion Superconducting Quantum Metamaterial: Towards Quantum-level Switching

“…At such intensity the current density in the outer perimeter of the disk will be of the order of 10 4  A/cm 2 . This is much smaller than the critical current density of the wire, which is approximately32 10 6  A/cm 2 at T = 77 K.…”

Demonstration experiments for solid-state physics using a table-top mechanical Stirling refrigerator

“…In this scenario, a long time can be several seconds for some low critical current density samples or even ms or µs for thin-film microbridges. The importance of these aspects and the need of a fast acquisition system which applies short current pulses is remarked, for instance, in references [12,13,14].…”

“…Both pistons (2) reciprocate inside the cylinders (1), so the gas is forced through two channels (10) which feed an expander-regenerator assembly (( 8) and ( 9)). Its driving plunger (11) is tied to a spring compensation system (12), allowing negligible spurious vibrations. Two magnetic motors (3) produce the reciprocation of the pistons.…”