Dynamics and thermal instability of magnetic flux in type-II superconductors

Abstract

In recent experiments, trapped magnetic flux is initially generated by abrupt laser heating of a strip of a type-II superconducting film subjected to a weak magnetic field. We study herein the nonequilibrium penetration of the flux into the Meissner state area. Effects of the heat dissipation and transport on the motion and stability of the interface between the magnetic flux and flux-free domains are considered. It is shown that the magnetic induction and the temperature have the form of a shock wave moving with constant velocity as large as that corresponding to the depairing current. In the vicinity of the front, superconductivity is suppressed by strong screening currents. The front velocity is determined by the Joule heat caused by the electric current in the normal domain at the flux front. The stability of the shock wave solution is investigated both analytically and numerically. For sufficiently small heat diffusion constant a finger shaped thermal instability is found.

Flux-flow instability in a strongly disordered superconducting strip with an edge barrier for vortex entry

“…We find that E q does not depend on w and I q scales linearly with the width of the strip (when w is much larger than the width of the region with current density gradient near the edge where the vortices enter the strip). This result coincides with the expectations following from the spaceaveraged models [4,7,[11][12][13][14] with no edge barrier effect. Quantitative comparison (for the dependence of E q and I q on magnetic field or material parameters) with these models is impossible, because only in [11] are both Joule heating and the effect connected with finite τ Δ taken into account.…”

“…In previous theoretical models [7,[11][12][13][14] the temperature of the electrons T e was calculated from the balance between the spatially and time-averaged Joule dissipation and the heat removal to the substrate, which eliminates the discrete nature of the moving vortices. In our work we take into account both the local Joule heating and local cooling (due to the time variation of the magnitude of superconducting order parameter D | |), depending on the vortex position.…”

Thermal Mechanisms of Stable Macroscopic Penetration of Applied Currents in High Temperature Superconductors and their Instability Conditions

“…The limiting transition dI/dt→ 0, applying to the model described by equation (11), leads to the static zerodimensional heat balance equation. In this case, i. e. at ha/λ << 1, uniform static thermal state of the superconducting slab is the solution of the following equation…”

“…(4) shows the influence of the current charging rate on the thermo-electrodynamics states of the superconducting slab under consideration cooled at operating temperature T 0 = 20 K. The numerical simulation was performed under the assumption of the nonintensive cooling condition (h=10 -3 W/(cm 2 ×K) at B=10 T and the critical current density is described by equation (9) with parameters (10). This allows one to use the transient and static zero-dimensional models (11) and (12). Accordingly, solid lines 2-4 describe the transient thermo-electrody- Fig.…”

“…The numerous previous investigations of the magnetic instabilities in high-T c superconductors have been made [3][4][5][6][7][8][9][10][11][12]. In the meantime, basic features of the stable charging of applied current into high-T c superconductors, especially, influence of thermal mechanisms on the electrodynamics state formation have still not discussed.…”