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 ξ. 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.
|Physical Review B - Condensed Matter and Materials Physics
|Published - 24 Feb 2012