Phase slip centers in a two-band superconducting filament: application to MgB2

Within the framework of non-stationary Ginzburg-Landau equations generalized on a case of two order parameters, we investigated dynamic characteristics of two-band superconducting MgB2 filaments in a voltage-driven regime. We calculated current-voltage characteristics of superconducting MgB2 filaments with different lengths and compared with single-band superconductor of corresponding sizes. Despite the presence of two interacting bands for small values of a ratio of effective Cooper pairs weights, phenomenological constants of diffusion and large lengths of channels the well-known S-form of current-voltage characteristic for the single-band superconductor with fluctuations of the current density in a certain interval of the voltage also takes place in the case of two-band superconductor. Analysis of spectra of the current density and the time-evolution of order parameters for long channels points out that such unusual forms of current-voltage characteristics are caused by the occurrence either chaotic oscillations of order parameters modules or the interference of some their oscillation modes. The further increase of the ratio of effective weights of Cooper pairs and phenomenological constants of diffusion smoothes these oscillations and transforms the system in an ordered state, where the S-form of current-voltage characteristics becomes more flattened. The latter can be the feature of two-band superconducting long channels.
10 pages, 4 figures, revised version