Nonequilibrium vortex-density-wave state in two-dimensional superconductors

Abstract

A numerical study of nonuniform current flow in a two-dimensional superconductor suggests that current-depaired vortices and antivortices can form a stable nonequilibrium vortex-density-wave state. A necessary condition for generating vortex density waves is a dc current distribution that displays a pronounced symmetrical dip along the direction of equipotential lines. When the depth of the current density profile exceeds a crossover depth, the stationary densities of vortices and antivortices evolve into two coupled density waves which travel in opposite directions. For relatively deep current profiles, the density waves produce local-density oscillations whose frequency increases linearly with increasing current profile depth. A dip in the current density profile can be induced in two-dimensional superconducting In−InOx films that use a special geometry of long-line inhomogeneities. As the dc current increases above a threshold, the measured voltage spectra display peaks which grow and shift toward higher radio frequencies. The detected spectral peaks, whose frequency increases linearly with current, result from the periodic motion of current-depaired vortex density waves.

Source-reported materials — not catalogue approval

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