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

Abstract

Within the framework of non-stationary Ginzburg–Landau equations generalized to the 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 of different lengths and compared with a single-band superconductor of corresponding sizes. Despite the presence of two interacting bands for small values of the 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 voltage also takes place in the case of the two-band superconductor. An analysis of spectra of the current density and the time-evolution of the order parameters for long channels points out that such unusual forms of current–voltage characteristics are caused by the occurrence of either chaotic oscillations of the moduli of the order parameters or the interference of some of their oscillation modes. A further increase in the ratio of effective weights of the Cooper pairs and in phenomenological constants of diffusion smoothes these oscillations and transforms the system into an ordered state, where the S-form of current–voltage characteristics becomes more flattened. The latter can be a distinctive feature of two-band superconducting long channels.