arXiv subjects

D. Yu. Vodolazov

Publications and source records attributed to D. Yu. Vodolazov.

39 records · Page 3Linked to original sources

arXiv2001

Vortex entry conditions in type-II superconductors. Effect of surface defects

The conditions for the entry of vortices into type-II superconductors being in the Meissner and/or mixed state, are studied by both numerical and analytical solution of the Ginzburg-Landau equations. A modulation instability of the superconducting order parameter is shown to occur when the kinematic momentum (or supervelocity) of the condensate reaches a threshold value at the superconductor edge or surface. Due to this instability, vortices start to nucleate at the edge or surface and then penetrate deeper into the sample. It is found that the presence of surface defects causes a noticeable drop of the first penetration field and leads to a qualitative change of the magnetization curve. Based on these results a simple phenomenological model of the edge or surface barrier, taking into account the effect of surface defects, is suggested.

cond-mat.supr-con↗

arXiv2000

Distribution of the magnetic field and current density in superconducting films of finite thickness

A one-dimensional equation describing the distribution of the effective vector potential $\bar A(y)$ across a film width, which holds for thin ($d<λ$) and thick ($d>λ$) films alike, is derived based on the analysis of a 2D Maxwell-Londons equation for superconducting films in a perpendicular magnetic field. The validity of this equation for a finite-thickness film is verified by a numerical analysis. An approximation dependence $\bar A(y)$, finite (with all of its derivatives) across the entire film width, is found for films, being in the Meissner state. The flux-entry field is evaluated for a film of arbitrary thickness. An approximation expression is obtained for the distribution of the sheet current density in the mixed state of a pin-free superconducting film with an edge barrier. The latter approximation allows to estimate magnetic field concentration factor at the film edge as a function of external magnetic field and geometrical parameters of the sample.

cond-mat.supr-con↗

arXiv1999

Magnetization curves and ac susceptibilites in type-II superconductors: geometry-independent similarity and effect of irreversibility mechanisms

The magnetic characteristics for superconducting samples of different geometries (plates and films of various widths) and orientation with respect to external field are compared. A similarity is established between the magnetization curves M(H) and the corresponding susceptibilities. A sign reversal is predicted for the 3rd harmonic of the ac susceptibillity when the irreversibility mechanism changes from bulk pinning to edge barrier. A mutual influence of the edge barrier and bulk pinning on the magnetization curves and field-dependent ac susceptibility is studied on the basis of an exactly solvable model (narrow plate in a parallel field and/or narrow film in a perpendicular magnetic field).

cond-mat.supr-con↗