Collective modes of anisotropic narrow-band Bloch-electron superconductors with nearest-neighbor pairing interaction

Susumu Misawa

doi:10.1103/PhysRevB.50.16623

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Collective modes of anisotropic narrow-band Bloch-electron superconductors with nearest-neighbor pairing interaction

Susumu Misawa

DOI 10.1103/PhysRevB.50.16623 · Physical Review B

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Abstract

On the basis of the phenomenological tight-binding model with the intersite pairing interaction, the collective modes of the anisotropic narrow-band superconductors consisting of Bloch electrons are investigated within the ladder-diagram approximation with the vacuum-polarization correction. For the extended s- and d-wave states on a two-dimensional square lattice, the velocity of the sound mode for the artificial neutral system and the energy of the plasma mode for the charged system are calculated as functions of hole density at T=0. Both of them depend on hole and electron densities symmetrically, and are almost unaffected by the anisotropy of the order parameter. The main term in the sound-velocity expression is shown to have the generalized form of the standard hydrodynamic expression. The plasma-energy expression almost coincides with that for the normal-state Bloch electrons. Possible additional approximations are examined.