In this work, we studied the dynamics of the kinematic vortices (kV) in a mesoscopic superconductor under the influence of external applied magnetic fields (H) and transport currents (J tr ). A J tr (H ) phase diagram is determined. We show that the vortex dynamics are profoundly affected by the presence of constrictions and by H. We find that between the Meissner and normal states, the resistive state is comprehended by three distinct states. One of these states is a kinematic vortex-antivortex pair for low values of H. For moderate values of fields, the kV state is unpaired and only a single kinematic vortex exists. In the high field regime, the kinematic vortex becomes an Abrikosov-like state with a lower velocity. It was also shown that for tenths of picoseconds, a surface barrier effect acts over the instantaneous velocity of the kV.

In this work we solved the time dependent Ginzburg-Landau equations to simulate homogeneous superconducting samples with square geometry for several lateral sizes. As a result of such simulations we notice that in the Meissner state, when the vortices do not penetrate the superconductor, the response of small samples are not coincident with that expected for the bulk ones, i.e., 4πM = −H. Thus, we focused our analyzes on the way which the M(H) curves approximate from the characteristic curve of bulk superconductors. With such study, we built a diagram of the size of the sample as a function of the temperature which indicates a threshold line between macroscopic and bulk behaviors. AbstractIn this work we solved the Time-Dependent Ginzburg-Landau equations to simulate homogeneous superconducting samples with square geometry for several lateral sizes. As a result of such simulations we notice that in the Meissner state, when the vortices do not penetrate the superconductor, the response of small samples are not coincident with that expected for bulk ones, i.e., −4πM = H. Thus, we focused our analyzes on the way which the M(H) curves approximate from the characteristic curve of bulk superconductors. With such study, we built a diagram of the size of the sample as a function of the temperature which indicates a threshold line between macroscopic and bulk behaviors.

Usually, the measurements of electronic and magnetic properties of superconducting samples are carried out under a constant temperature bath. On the other hand, thermal gradients induce local variation of the superconducting order parameter, and the vortex dynamics can present interesting behaviors. In this work, we solved the time-dependent Ginzburg-Landau equations simulating samples under two different thermal gradients, and considering two values of the Ginzburg-Landau parameter, κ. We find that both parameters, i.e. κ and thermal gradients, play an important role on the vortex dynamics and on the magnetization behavior of the samples.

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