Superconductivity assisted by interlayer pair hopping in multilayered cuprates
In order to explore why the multilayered cuprates have such high ${T}_{\text{c}}$ values, we have examined various interlayer processes. Since the interlayer one-electron hopping has little effect on the band structure, we turn to the interlayer pair hopping. The superconductivity in a double-layer Hubbard model with and without the interlayer pair hopping, as studied by solving the Eliashberg equation with the fluctuation exchange approximation, reveals that the interlayer pair hopping acts to increase the pairing interaction and the self-energy simultaneously, but that the former effect supersedes the latter and enhances the superconductivity, along with how the sign of the interlayer off-site pair hopping determines the relative configuration of $d$ waves between the adjacent layers. Study of the triple-layer case with the interlayer pair hopping further reveals that the superconductivity is further enhanced but tends to be saturated toward the triple-layer case.