Surface barrier in mesoscopic type-I and type-II superconductors -: art. no. 144529

We study the surface barrier for magnetic-field penetration in mesoscopic samples of both type-I and type-II superconductors. Our results are obtained from numerical simulations of the time-dependent Ginzburg-Landau equations. We calculate the dependence of the first field for flux penetration (H-p) with the Ginzburg-Landau parameter (kappa) observing an increase of H-p with decreasing kappa for a superconductor-insulator boundary condition [(del-iA)Psi\(n)=0] while for a superconductor-normal boundary condition (approximated by the limiting case of Psi\(S)=0) H-p has a smaller value independent of kappa and proportional to H-c. We study the magnetization curves and penetration fields at different sample sizes and for square and thin-film geometries. For small mesoscopic samples we study the peaks and discontinuous jumps found in the magnetization as a function of magnetic field. To interpret these jumps we consider that vortices located inside the sample induce a reinforcement of the surface barrier at fields greater than the first penetration field H-p1. This leads to multiple penetration fields H-pi=H-p1,H-p2,H-p3,... for vortex entrance in mesoscopic samples. We study the dependence on sample size of the penetration fields H-pi. We explain these multiple penetration fields, extending the usual Bean-Livingston analysis by considering the effect of vortices inside the superconductor and the finite size of the sample.