Current states and band spectrum of a condensate in superconducting superstructures

The dependence of the current on the “macroscopic quasimomentum” ps in a system with periodically varying order parameter in space is investigated (superconducting superstructure). This dependence has the nature of a non-monotonic function which vanishes every time the quasi-momentum is a multiple of the quantity πℏ/a (a is the superstructure period). There is a finite number of bands (branches) of the functions j = jn(ps) and energies E = En(ps) whose number is of the order of pca/ℏ where pc is the critical momentum of breaking the homogeneous current state. The function j(ps) becomes single-valued upon achievement of the threshold degree of modulation of the superlattice order parameter, namely, in this case qualitative distinctions between the band pattern and the homogeneous current state occur.

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