Journal de Physique IV vol:6 issue:C3 pages:335-343
The mixed state in homogeneous type-II superconductors is characterized by the formation of a lattice consisting of flux lines (FL) each carrying one flux quantum phi(0). To make the penetration of these quantized FL into a superconductor possible, normal vortex cores must be created. At the upper critical field H-c2(T) the total area of the normal cores formally coincides with the sample area and the superconductivity is completely destroyed. To reduce the destructive action of magnetic field on superconductivity, one should separate the areas where flux penetrates from these where the superconducting order parameter psi nucleates. Using nanostructuring and fabricating a lattice of microholes (''antidots'') to let flux go through antidots, we are thus helping the order parameter between the antidots to sustain much higher currents and magnetic fields. This is the main idea of ''quantum design'' of the two important superconducting parameters: the critical current jc(T,H) and the critical field H-c2(T). By optimizing the parameters of the antidot lattices, we have stabilized multi-quanta vortex lattices and we have drametically increased j(c)(T,H), up to values limited by the depairing current, and strongly enhanced the critical field, which can eventually be much higher than H-c2(T) of the built reference superconducting material.