Mesoscopic superconducting disks

Using the nonlinear Ginzburg-Landau (GL) equations, type I superconducting disks of finite radius (R) and thickness (d) are studied in a perpendicular magnetic field. Depending on R and d, first- or second-order phase transitions are found for the normal to superconducting state. For sufficiently large R, several transitions in the superconducting phase are found corresponding to different angular momentum giant vortex states. In an increasing magnetic field the superconductor is in its ground state, while in a field down sweep it is possible to drive the system into metastable states. We also present a quantitative analysis of the relation between the detector output and the sample magnetization. The latter, and the incorporation of the finite thicknesses of the disks, are essential in order to obtain quantitative agreement with experiment. (C) 1999 Academic Press.