Browsing by Author "Shapiro, BY"

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Alternating para/diamagnetic domains in a p-wave superconductor
(2003-11-01)
Bel, G
;
Rosenstein, B
;
Shapiro, BY
;
Shapiro, I
;
電子物理學系
The mesoscopic one-dimensional magnetic texture caused by small Zeeman coupling in a p-wave superconductor in the magnetic field is found. The field orientation is opposite on the two sides of the texture and the magnitude can be even smaller than H-c1. The texture is not built from various singular topological defects, like vortices, as previously found in the simplest three-component Ginzburg-Landau model of superconductors.
Dynamics and thermal instability of magnetic flux in type-II superconductors
(2005-05-01)
Shapiro, BY
;
Shapiro, I
;
Rosenstein, B
;
Bass, F
;
電子物理學系
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 heal 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.
Fluctuations in single-crystal YBa2Cu3O6.5: Evidence for crossover from two-dimensional to three-dimensional behavior
(2001-04-01)
Rosenstein, B
;
Shapiro, BY
;
Prozorov, R
;
Shaulov, A
;
Yeshurun, Y
Magnetization measurements as a function of temperature are reported for YBa2Cu3O6.5 crystal (T-c = 45.2 K) for fields between 0.2 and 3.5 T. All isochamps for H > 1 T intersect at T-2D(star) similar or equal to 42.8 K, implying a fluctuation contribution to the magnetization. These curves collapse into a single curve when magnetization and temperature are scaled according to the predicted "two-dimensional (20) scaling" in the fluctuation regime. Surprisingly, the low-field curves also intersect, at T-3D(star) similar or equal to 43.4 K, and they obey a 3D scaling. We provide a theoretical picture of the magnetization in the fluctuation regime based on the Lawrence-Doniach model. Within this model we calculate the field and temperature dependence of the magnetization. The two intersection points and the 2D --> 3D crossover are consistent with the experimental observation.
Shock waves and avalanches in type-II superconductor
(2005-05-01)
Rosenstein, B
;
Shapiro, BY
;
Shapiro, I
;
電子物理學系
;
Department of Electrophysics
The rapid penetration of magnetic flux into a Meissner phase of the type-II superconductor is studied analytically and numerically. A sharp shock wave front of the magnetic induction is formed due to the singularity of the resistivity at the transition from the mixed to the normal state. It is shown that current densities at the front reach high values, of the order of the depairing current density. The 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. The shock wave magnetic induction and the temperature profiles move with constant velocity determined by the Joule heat produced by the electric current in the normal domain at the flux front. The stability of the shock wave solution is investigated. For a sufficiently small thermal-diffusion constant, a finger-shaped avalanche instability appears.
Unconventional vortices in multicomponent Ginzburg-Landau theory
(2002-06-01)
Pechenik, E
;
Rosenstein, B
;
Shapiro, BY
;
Shapiro, I
;
電子物理學系
Simulations of a three-component time-dependent Ginzburg-Landau (Abelian Higgs) model reveals that the dominant topological defects are vector vortices rather than conventional Abrikosov (Nielsen-Olesen) vortices or skyrmions. We describe in detail these vortices in the steady state and discuss their possible role in the dynamics. In particular, we conclude that the vector vortices have a superconducting core distinct from the superconducting bulk state. The profile of the vector order parameter and the magnetic field are calculated.