5 July 1996 Band states of the condensate in superconducting superlattices
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Abstract
We have studied theoretically a superconducting system with the order parameter periodic in space. The period of such a superconducting superlattice (SS) should be of the order of the coherence length (xi) (T), so that it is a macroscopic value in comparison with the atomic scale. The spectrum of the condensate in such structures becomes of the band type with a finite number of energy bands. Splitting of the spectrum of the condensate into the allowed and forbidden energy bands starts from a certain threshold level of modulation of the order parameter by the superlattice. In view of periodicity of the system, the current states of the condensate in excited bands at higher values of energy can exist in principle along with the conventional Josephson current, corresponding to the lowermost energy band. The presence of the SS energy bands makes possible the transitions of the condensate as a macroscopic system from one quantum state to another. A set of equations in the framework of the Ginzburg-Landau scheme has been obtained and current-phase relations for a SS have been calculated. The crossover from the Josephson-like behavior of a SS (the high value of the constant (lambda) , characterizing suppression of the superconducting order parameter) to the homogeneous current-carrying state has been investigated. It has been shown, that as (lambda) decreases, the maximum superconducting SS current is displaced to a range of a lower value of the phase difference in the lattice period. We study the band states stability of the SS.
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Gurami Alexandrov Gogadze, "Band states of the condensate in superconducting superlattices", Proc. SPIE 2697, Oxide Superconductor Physics and Nano-Engineering II, (5 July 1996); doi: 10.1117/12.250285; https://doi.org/10.1117/12.250285
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