Dynamical properties of superconducting nanowires

The dynamical properties of thin superconducting wires (nanowires) are studied using numerical simulations based on a one-dimensional time-dependent Ginzburg-Landau equation, which is modified by introducing an order parameter u characterizing the 'purity' of the superconductor material. It is established that relatively long nanowires (with lengths much greater than the coherence length) made of a 'pure' superconductor (u > 1) are characterized by two critical current density values: j{sub c1} and j{sub c2}. For j < j{sub c1}, the total current is entirely superconducting, whereas for j > j{sub c2}, the current is purely normal. In the intermediate region of current densities, j{sub c1} < j < j{sub c2}, the total current contains both superconducting and normal components (mixed state) and the nanowire exhibits the generation of high-frequency electromagnetic waves. The current-voltage characteristics are constructed and the radiation spectrum is obtained. The properties of short superconducting nanowires (with lengths on the order of the coherence length) coincide with those of the Josephson junction. In the case of an 'impure' superconductor (u < 1), the nanowire is characterized by a single critical current density.