Collective oscillations of the order parameter in superconductors with local pairs

Collective oscillations of the order parameter in superconductors with local singlet pairing are studied. It is shown that for an uncharged superfluid liquid there exist oscillations with an acoustic spectrum, analogous to the Anderson–Bogolyubov oscillations in the BCS theory. Taking into account the long-range part of the Coulomb interaction gives a plasma threshold in the spectrum of oscillations. If, however, there exists, in addition to a narrow band, whose electrons form local pairs, a wide conduction band, then the spectrum once again becomes gapless.

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