Interlayer pair hopping: Superconductivity from the resonating-valence-bond state

Superconductivity in the high-$T_c$ materials is interpreted as 〈$e_k$ $e_{\mathrm{-}k}$〉 condensation of hole bosons. Coherent interlayer tunneling of boson pairs results in order-parameter equations which are quite different from those of the Bardeen-Cooper-Schrieffer theory. A model is presented which suggests how this condensation is affected by charge-carying boson interactions.