Browsing by Author "Berco, D."

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Current carrying vortex crystals
(2012)
Rosenstein, B.
;
Shapiro, I.
;
Berco, D.
;
Shapiro, B. Ya
;
電子物理學系
Abrikosov vortices in a type-II superconducting film subjected to strong magnetic field B with periodic array of nanoholes of the density n(pin) form sometimes a vortex crystal, even when they are driven by a transport current. It is shown numerically that the crystal melting and transition to the resistive state occurs as a coherent depinning of the single vortex dislocations. For a system with interstitial vortices, f = B/Phi(0)n(pin) > 1, the mechanism of depinning depends on the current direction with respect to the pinning array. It was found that slightly above the critical current trajectories of moving vortices are not straight, but rather acquire a snake - like shape enveloping the system of pins. In contrast to the matching field case, f = 1, the transition to a resistive state is not coherent and is developing through formation of the "snake - like" vortex trajectories. It is pointed out that the depinning is closely associated with the appearance of a strongly varying electric field. We calculated the electric fields accompanying vortex crystal melting and found the voltage-current characteristics. When the pinning array is made random, the critical current is reduced.
Electrodynamics of type-II superconductor with periodic pinning array
(2011-01-01)
Hung, R. F.
;
Berco, D.
;
Shapiro, I. Ya
;
Shapiro, B.
;
Rosenstein, B.
Static and dynamic distribution of the superconducting condensate order parameters and current density is studied by numerical simulation of the 2D time-dependent Ginzburg-Landau equations The vortex flux lattice in layered type-II superconductors under magnetic field above the lower critical field is described by the order parameters Moreover the pinning effect has been considered in this work The Abrikosov lattice which is hexagonal in the static case is deformed due to the size of pinning centers The dynamical order parameters distribution shows that the vortex transport (flux flow) is conducted via diffusive motion of the so-called interstitial vortices The trajectories for interstitial vortices with different sizes of pinning centers are shown (C) 2010 Elsevier BV All rights reserved
Extended object tunneling: Current-carrying states of Abrikosov vortices in a superconductor with artificial nanobarriers
(2012-02-24)
Rosenstein, B.
;
Shapiro, I.
;
Shapiro, B. Ya.
;
Li, Dingping
;
Frydman, A.
We consider the structure and dynamics of two-dimensional fluxons created by a magnetic field in a type-II superconductor film with critical temperature T-1 in the presence of nanostripes of material with a higher critical temperature T-2. The width of the stripes is of the order of the coherence length xi. Such a stripe plays the role of a potential barrier for vortices. When subjected to the current J parallel to the stripe, vortices move toward the barrier. Below the critical current J(c), the flux flow is effectively halted by the barrier, while above J(c), flux penetrates the stripe and passes the barrier. The mechanism of the barrier penetration ("soliton tunneling" occurs even at zero temperature) is rather unusual: the vortices adjust their shape, and upon passing the barrier, they shrink their cores. The critical current and the I-V curves are calculated numerically and analytically using variational approach.
Glass transition and the replica symmetry breaking in vortex matter: MC study
(2011-01-01)
Li, Dingping
;
Rosenstein, B.
;
Chen, Shou
;
Lin, H. H.
;
Berco, D.
We investigate effects of disorder and thermal fluctuations on the Abrikosov state of type II superconductors applying the Monte Carlo method to Ginzburg-Landau theory to confirm earlier replica calculation The vortex phase diagram has two transition lines the melting line and the vortex glass transition lines in both crystalline and homogeneous states The glass line is always a continuous transition while the melting line is the first order (C) 2010 Elsevier BV All rights reserved