Critical current of Nb, NbN, and TaN thin-film bridges with and without geometrical nonuniformities in a magnetic field

The dependence of the critical current I-C on magnetic field has been systematically studied in thin-film superconducting Nb, NbN, and TaN bridges with widths smaller than the Pearl length. We have shown that application of a magnetic field of a proper orientation to the bridges with bends results in a suppression of the current crowding effect. This leads to an increase up to about 30% of the critical current in such bridges with respect to I-C measured at zero magnetic fields. We have demonstrated a good qualitative and quantitative agreement between experimental results and theoretical predictions obtained in frame of the London and Ginzburg-Landau models for a dominating edge pinning mechanism of vortices. Also we observed oscillations of I-C at magnetic fields, which increase with a decrease of the width of superconducting stripe. These oscillations are qualitatively similar to the Fraunhofer-like dependence of a critical current on the magnetic field in wide Josephson junctions. In the frame of theGinzburg-Landau model, a penetration and pining of vortex chain is considered as a mechanism responsible for this nonmonotonic behavior of the critical current.