scholarly journals Dynamics of two-dimensional pancake vortices in layered superconductors

1996 ◽  
Vol 53 (1) ◽  
pp. 449-456 ◽  
Author(s):  
A. S. Mel’nikov
Keyword(s):  
Two Dimensional ◽  
Layered Superconductors ◽  
Pancake Vortices

scholarly journals Reentrant dynamics of driven pancake vortices in layered superconductors

2016 ◽  
Vol 94 (2) ◽  
Author(s):  
H. J. Zhao ◽  
Wenjuan Wu ◽  
Wei Zhou ◽  
Z. X. Shi ◽  
V. R. Misko ◽  
...  
Keyword(s):  
Layered Superconductors ◽  
Pancake Vortices

scholarly journals Time-Correlated Vortex Tunneling in Layered Superconductors

2017 ◽  
Author(s):  
John H. Miller Jr. ◽  
Martha Y. S. Villagrán
Keyword(s):  
Piecewise Linear ◽  
Threshold Current ◽  
Critical Currents ◽  
Pair Creation ◽  
Coated Conductors ◽  
Layered Superconductors ◽  
High Tc ◽  
Tunneling Matrix Element ◽  
Pancake Vortices ◽  
Abrikosov Vortices

The nucleation and dynamics of Josephson and Abrikosov vortices determine the critical currents of layered high-Tc superconducting (HTS) thin films, grain boundaries, and coated conductors, so understanding their mechanisms is of crucial importance. Here we treat pair creation of Josephson and Abrikosov vortices in layered superconductors as a secondary Josephson effect, in which each full vortex is viewed as a composite fluid of micro-vortices, such as pancake vortices, which tunnel coherently via a tunneling matrix element. We introduce a two-terminal magnetic (Weber) blockade effect that blocks tunneling below a threshold current, and simulate time-correlated vortex tunneling above threshold. The model shows nearly precise agreement with voltage-current (V-I) characteristics of HTS cuprate grain boundary junctions, which becomes more concave rounded as temperature decreases, and also explains the piecewise linear V-I behavior observed in iron-pnictide bicrystal junctions and other HTS devices. When applied to either Abrikosov or Josephson pair creation, the model explains a plateau seen in plots of critical current vs. thickness of HTS coated conductors. The observed correlation between theory and experiment strongly supports the proposed quantum picture of vortex nucleation and dynamics in layered superconductors.

Superconducting Fractal Multilayers

Fractals ◽  
1997 ◽  
Vol 05 (supp02) ◽  
pp. 101-117
Author(s):  
A. S. Sidorenko
Keyword(s):  
Magnetic Field ◽  
Angular Dependence ◽  
Fractal Dimensionality ◽  
High Energy ◽  
Critical Magnetic Field ◽  
Superconducting Film ◽  
Two Dimensional ◽  
Layered Superconductors ◽  
Upper Critical Magnetic Field ◽  
Critical Magnetic Fields

The influence of fractal geometry on superconductivity has been studied for layered superconductors. Superconducting multilayers consisting of alternating Nb and Cu layers with fractal stacking sequence and fractal dimension Df=0.63 including the two limiting cases Df= 0 (single superconducting film) and Df=1 (periodic multilayers) were prepared by electron-beam evaporation in ultrahigh vacuum. The layers of Nb and Cu were put down alternately via computer control of the target shutter. The structure of the samples has been checked with in situ reflection high-energy electron diffraction (RHEED) and Auger depth profiling, confirmed the prescribed layering geometry. Superconductivity was investigated by measurements of the critical temperature of superconducting transition Tc, and of the temperature and of the angular dependence of the upper critical magnetic fields Bc2. The observed dependences of Tc on the parameters of fractal samples are in a good qualitative agreement with the proximity effect theory developed for layered superconductors with a self-similar fractal structure. The behavior of the upper critical magnetic field is directly related to the type of the layering. At low temperatures, all samples show the same two-dimensional behavior essentially governed by the topological dimension of the individual superconducting layers, independent of the fractal dimensionality Df of the samples, whereas for temperatures near Tc the type of layering determines the dimensionality, resulting in a multicrossover behavior of fractal samples. The angular dependence of the upper critical magnetic field Bc2(θ) of fractals corresponds to the theory for a two-dimensional superconductor at all temperatures, reflecting the multicrossover behavior of the fractal multilayers, as long as the temperature-dependent coherence length is comparable with a certain scale of fractal.

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