Extended object tunneling: Current-carrying states of Abrikosov vortices in a superconductor with artificial nanobarriers

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.