Saddle point states in two-dimensional superconducting films biased near the depairing current

D. Y. Vodolazov

doi:10.1103/PhysRevB.85.174507

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Saddle point states in two-dimensional superconducting films biased near the depairing current

D. Y. Vodolazov

DOI 10.1103/PhysRevB.85.174507 · Physical Review B

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Abstract

The structure and energy of saddle point (SP) states in a two-dimensional (2D) superconducting film of finite width w with transport current I are found in the framework of the Ginzburg-Landau model. We show that very near the depairing current Idep, a SP state with a vortex does not exist; it transforms to a 2D nucleus state, which is a finite region with partially suppressed order parameter. It is also shown that for slightly lower currents the contribution of the vortex core energy is important for a SP state with a vortex and it cannot be neglected for I≳0.6Idep. It is demonstrated that in a film with local current concentration near a bend, the energy of the SP state may be much smaller than that in the straight film, and this favors the effect of fluctuations in such samples.