Thin superconductors and SQUIDs in perpendicular magnetic field

Brandt, Ernst Helmut

doi:10.1103/physrevb.72.024529

Cited by 72 publications

(82 citation statements)

References 22 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…However, it might also be used for a very thin superconducting film of thickness d, provided that the effective penetration length ⌳ =2 2 / d is larger than the lateral dimensions L of the film. 16,17 In this scenario, the z component of the magnetic film outside the film is nearly the same as the applied magnetic field, so the demagnetization factor can be neglected. The dimensions of the samples used in the present work are within this limit.…”

Section: ͑2͒mentioning

confidence: 99%

Vortex-antivortex annihilation dynamics in a square mesoscopic superconducting cylinder

et al. 2009

View full text Add to dashboard Cite

The dynamics of the annihilation of a vortex-antivortex pair is investigated. The pair is activated magnetically during the run of a simulated hysteresis loop on a square mesoscopic superconducting cylinder with an antidot inserted at its center. We study the nucleation of vortices and antivortices by first increasing the magnetic field, applied parallel to the axis of the sample, from zero until the first vortex is created. A further increase in the field pulls the vortex in, until it reaches the antidot. As the polarity of the field is reversed, an antivortex enters the scene, travels toward the center of the sample, and eventually the pair is annihilated. Depending on the sample size, its temperature, and Ginzburg-Landau parameter, the vortex-antivortex encounter takes place at the antidot or at the superconducting sea around it. The position and velocity of the vortex and antivortex singularities were evaluated as a function of time. The current density, magnetization, and orderparameter topology were also calculated. Achieving a deep understanding of the nucleation and propagation of vortices in real superconductors is a truly complex task, since these entities interact with almost everything: first, with the surface of the specimen, to surpass it; upon entrance, with other vortices that might have already penetrated, and also with defects, which might attract them and even act as pinning centers. Additional difficulties to emulate the problem arise from the fact that vortices generate heat while propagating, what can be harmful to the robustness of the superconducting properties, if not catastrophic, as is the case of vortex avalanches observed in some superconducting films. [1][2][3][4][5][6] It is quite common, however, that the existence of pinning potentials represent a beneficial feature, since vortices can thus be prevented from undergoing dissipative motion. An interesting approach to the problem, which enables one to address most specificities without excessive complexity, is to work in the small universe of mesoscopic samples. In such an ambient, one can accommodate the essential ingredients: relatively important surface-tovolume ratio, only a few vortices on scene, and a number of defects-the so-called antidots-usually arranged in a regular pattern. Furthermore, one can study the interaction of an individual vortex-antivortex ͑V-AV͒ pair and, eventually, witness their mutual annihilation.Recently, there have been many studies about V-AV configurations in mesoscopic superconductors ͑see for instance Refs. 7-11͒. The authors of these references have found that vortices and antivortices may coexist in equilibrium in configurations which look like a V-AV molecule. A somewhat common approach is to assume an a priori configuration and minimize the free energy in terms of some relevant parameter for which the V-AV molecule is a stable configuration. Here, we will focus in a rather different approach concerning more with the dynamics of a V-AV encounter. The aim of the present work is to elucidate the de...

show abstract

Section: ͑2͒mentioning

confidence: 99%

Vortex-antivortex annihilation dynamics in a square mesoscopic superconducting cylinder

et al. 2009

View full text Add to dashboard Cite

show abstract

“…In such a case, still H = H a and the resulting magnetic diffraction pattern will be interior of the junction and so generating a magnetic field H in the barrier plane such that j s = ẑ ϫ H. The problem of finding the j s distribution in a single superconducting field subjected to a transverse magnetic field has been analytically solved for different film geometries. 7,8 However, a planar JTJ is made by two overlapping superconducting films separated by a thin dielectric layer and the Meissner current distributions on the interior surfaces ͑top surface of the bottom film and bottom surface of the top film͒ require numerical approaches even for the more tractable electrode configurations. Recently, 9 the magnetic field distribution H Ќ in the barrier of small planar JTJs has been numerically obtained in the case when an external magnetic field is applied perpendicular to the barrier plane H a ϵ͑0,0,H z ͒.…”

Section: Introductionmentioning

confidence: 99%

Static properties of small Josephson tunnel junctions in an oblique magnetic field

et al. 2009

View full text Add to dashboard Cite

We have carried out a detailed experimental investigation of the static properties of planar Josephson tunnel junctions in presence of a uniform external magnetic field applied in an arbitrary orientation with respect to the barrier plane. We considered annular junctions, as well as rectangular junctions ͑having both overlap and cross-type geometries͒ with different barrier aspect ratios. It is shown how most of the experimental findings in an oblique field can be reproduced invoking the superposition principle to combine the classical behavior of electrically small junctions in an in-plane field together with the small junction behavior in a transverse field that we recently published ͓R. Monaco et al., J. Appl. Phys. 104, 023906 ͑2008͔͒. We show that the presence of a transverse field may have important consequences, which could be either voluntarily exploited in applications or present an unwanted perturbation.

show abstract

“…However, if the layer has a small but nonzero thickness d, the effective screening length becomes Λ ′ = 2λ 2 /d ≫ λ. 15,19 Λ ′ often exceeds the sample sizes considered in experiment and in such cases, the interaction is effectively logarithmic.…”

Section: Introductionmentioning

confidence: 99%

Biot-Savart correlations in layered superconductors

2009

View full text Add to dashboard Cite

We discuss the superconductor to normal phase transition in an infinite-layered, type-II superconductor in the limit where the Josephson coupling between layers is negligible. We model each layer as a neutral gas of thermally-excited pancake vortices and assume the dominant interlayer coupling is the electromagnetic interaction between the screening currents induced by these vortices. Our main result, obtained by exactly solving the leading order renormalization group flow, is that the phase transition in this model is a Kosterlitz-Thouless transition despite being a three-dimensional system. While the transition itself is driven by the unbinding of two-dimensional pancake vortices, an RG analysis of the low temperature phase and a mean-field theory of the high temperature phase reveal that both phases possess three-dimensional correlations. An experimental consequence is that the jump in the measured in-plane superfluid stiffness, a universal quantity in 2d KosterlitzThouless theory, receives a small non-universal correction (of order 1% in Bi2Sr2CaCu2O8+x). This overall picture places some claims expressed in the literature on a more secure analytical footing and resolves some conflicting views.

show abstract

Thin superconductors and SQUIDs in perpendicular magnetic field

Cited by 72 publications

References 22 publications

Vortex-antivortex annihilation dynamics in a square mesoscopic superconducting cylinder

Vortex-antivortex annihilation dynamics in a square mesoscopic superconducting cylinder

Static properties of small Josephson tunnel junctions in an oblique magnetic field

Biot-Savart correlations in layered superconductors

Contact Info

Product

Resources

About