We show that the resonating-valence-bond mechanism for high-$T_c$ superconductivity can lead to s-wave- and d-wave-like superconducting order parameters. The critical temperature for d-wave ordering is higher close to half-filling. At low temperatures, a mixture of d and s waves with a well-defined phase opens a full gap in the quasiparticle spectrum.

• Received 19 November 1987

DOI:https://doi.org/10.1103/PhysRevB.37.3664