Dynamics of the Abrikosov Vortices on Cylindrical Microtubes

We consider the special features at nano- and microscales of the vortex dynamics on superconducting cylindrical Nb tubes produced by the roll-up (self-rolling) technique. A transport current enters the tube through electrodes placed on both sides of a cut (in the paraxial direction) of the tube. The system is in the magnetic field perpendicular to the tube axis. The vortex dynamics is described by means of characteristic times: time (Delta t(1)) needed for a vortex to move from one edge of the tube to another and time (Delta t(2)) between two consecutive vortex nucleation events at one edge of the tube. A range of magnetic field values is analyzed where Delta t(1) as a function of the magnetic field has a highly nonlinear and non-monotonic behavior. For certain values of the magnetic field, two different trajectories are possible for a moving vortex, i.e., a bifurcation phenomenon occurs. We explain the reason of this bifurcation.