Interaction between novel vortices in nano-structured superconductors

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A simulation method for d-dot systems, which are composite structures of d- and s-wave superconductors, are developed, using two-components Ginzburug-Landau equations. Using this simulation, it is shown that interaction between two d-dot's becomes novel one and it depends on the distance and directions between them. Especially, fusion of two half-quantum fluxes occurs in short distance and it affects the interaction. Using this interaction, novel superconducting logic gates are proposed. And their operation is confirmed by the numerical simulations. Also it is shown that their operation speed is order of pico-second and d-dot logic circuit become good candidate for a computer of the next generation.A simulation method for investigation of microscopic properties of arbitrary shaped nano-sized superconductors is developed using the Bogoliubov-de Gennes equations. Using this method, interaction between two vortices is investigated. And a vortex molecule state is found. The quasi-particles … More around it show molecular orbital-like states. This property affect the interaction, which was believe to be purely repulsive from the phenomenological theory. This interaction affects the vortex configuration, in which the distance of vortices is rather short. Also quasi-particle structure around a giant vortex, which is peculiar to the nano-sized superconductors, is found to be different from that of a singly quantized vortex. Using similar method, it is shown that nano-sized anisotropic superconductors. have the modulated quasi-particle states in side of the energy gap, because of the confinement of the nodal states in the energy gap of anisotropic superconductors. These properties can be confirmed by the scanning tunneling spectroscopy experiment.Simulation method for dynamics of vortices in the superconducting networks is developed, by using combined one-dimensional and two-dimensional finite element method. Using this simulation method, it is shown that asymmetric finite superconducting networks shows ratchet effect, i.e. the vortex motion in these networks under external A.C. current causes D.C. voltage.Also vortex structure of random superconducting networks, which are models of porous superconductors, is investigated. Because of anomalous vortex pinning, which comes from their randomness, the transition temperature becomes low and vortices show peculiar structure. This result shows that such porous superconductors are good candidate for high Jc superconducting materials. Less