Confinement and quantization effects in nanosuperconductors

A systematic study of the geometry dependent nucleation of superconductivity in nanoscaled superconductors is presented in this paper. The experimental Τc(Η) phase boundary is compared to theoretical calculations obtained in the framework of the linearized Ginzburg-Landau theory for different geometries (square, triangle, disk). The influence of the transformation of a square into a rectangle on the Τc(Η) phase boundary is analyzed. In elongated rectangles, a crossover from a linear to a parabolic field dependence of Τc has been observed. The evolution of the superconducting state is studied in a perforated disk by varying the size of the hole. A transition from a one-dimensional to a two-dimensional regime is seen when increasing the magnetic field for disks with small holes.