Observation of Dynamic Interaction of Vortices with Pinning Centers by Lorentz Microscopy

Abstract

When a magnetic field penetrates a superconductor, it forms lattices of thin filaments called magnetic vortices. If a current is applied, these vortices move if not pinned down, destroying the superconductivity. The spatiotemporal behavior of the vortices was observed in a niobium film with a square lattice of defects made by ion irradiation. The vortices formed a domain of lattices. When the intensity of the applied magnetic field was decreased, the vortices were driven out of the film across its edges; when the intensity was increased, the vortices were driven into the film. The lattice exhibited brief and intermittent flow in "rivers" along domain boundaries. The rivers did not always flow along the same paths because new lattice domain configurations emerged whenever the flow stopped.

Simple model for plastic dynamics of a disordered flux-line lattice

“…This channel flow behavior has been observed experimentally using Lorentz microscopy [21]. Previous simulations of the coarse-grained BP model revealed results consistent with these and also showed that the channels can form a braided river which exhibit selfaffine (multifractal) behavior similar to fluvial braided rivers (see for example Ref.…”

“…These MD simulations do not, however, take into account a vortex density gradient, and do not agree with some the varieties of plastic dynamics observed in experiments. Section IV describes the original coarse-grained model, first used to describe vortex avalanches [4] and vortex rivers [19] as seen in experiments [20,21], and explains the exact model used here to describe the transport experiments summarized in Section II. To eliminate all potentially spurious sources of noise, a completely deterministic variant of the original BP model is used.…”

Vortex motion noise in micrometer-sized thin films of the amorphousNb0.7Ge0.3weak-pinning superconductor

“…That vortex motion can strongly depend on local conditions was demonstrated in Ref. 23, where it was found that, in the presence of pinning, vortices move in a form of intermittent ''rivers'' between the pinned islands. In our case one can hardly discuss a motion around the pinned islands, since any important pinned fraction would affect the average transport properties significantly, which is not observed ͑see the discussion of Fig.…”

Location-sensitive measurement of the local fluctuation of driven vortex density inBi2Sr2CaCuMaeda1, Tsuboi2, Abiru3 et al. 2002Phys. Rev. B243140View full textAdd to dashboardCite

“…In particular, various imaging techniques [17,21,22] have established the existence of various states of driven vortices in conventional superconductors. However, for high-T c superconductors, almost nothing has been clarified, since these probes are applicable only over a limited parameter range (temperature, magnetic field, and driving force) [23][24][25]. For high-T c superconductors, we chose a slightly different approach; local-density-noise (LDN) measurement [26][27][28].…”