Proceedings of the Second European Workshop on Low Temperature Electronics
J. Phys. IV France 06 (1996) C3-335-C3-343
Quantum Design of Superconducting Critical Parameters : Fundamental AspectsV.V. Moshchalkov1, M. Baert1, V.V. Metlushko1, E. Rosseel1, M.J. Van Bael1, K. Temst1, Y. Bruynseraede1 and R. Jonckheere2
1 Laboratorium voor Vaste-Stoffysica en Magnetisme, Katholieke Universiteit Leuven, Celestijnenlaan 200 D, 3001 Leuven, Belgium
2 Interuniversity Micro-Electronics Center, Kapeldreef 75, 3001 Leuven, Belgium
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 Φ0 . To make the penetration of these quantized FL into a superconductor possible, normal vortex cores must be created. At the upper critical field Hc2(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 Ψ 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 Hc2(T). By optimizing the parameters of the antidot lattices, we have stabilized multi-quanta vortex lattices and we have drametically increased jc(T,H), up to values limited by the depairing current, and strongly enhanced the critical field, which can eventually be much higher than Hc2(T) of the bulk reference superconducting material.
© EDP Sciences 1996