Interlayer pairings in the Josephson-coupled layered superconductors

Özet

The general expression for the effective pairing Hamiltonian is proposed to construct the multicomponent Ginzburg-Landau free energy functional for strongly anisotropic layered superconductors. Beside the one-particle interlayer direct tunneling, the coupling between layers occurs due to direct and exchange type attractive interaction in the particle-hole channel, also the attractive electron-electron (e-e) interaction in the particle-particle channel. Interlayer pairings in the particle-hole channel, as well as in the particle-particle channel are shown to enhance the critical temperature in the BCS approximation. The upper critical magnetic field $H_{C2}$ is studied for the superconductors under investigation. The interaction in the particle-particle channel is sensitive to a mag¬netic field parallel to superconducting layers and it has an influence to the upper critical field $H_{C2}$. It is shown that in the absence of the one-particle direct tunneling between layers the system becomes effectively two-dimensional in spite of the existence of interlayer e-e interactions. Hence, superconductivity becomes unstable with respect to the phase fluctuations of the order parameter.