d -wave pairing in the doped static charge-density-wave state on a two-dimensional square lattice

The extended Hubbard model with nearest-neighbor (NN) Coulomb repulsion is used to study superconductivity in a static charge-density-wave (CDW) state. It is found that the doped carriers form a large Fermi surface and are condensed into the dxy-wave superconducting state from the √2×√2 CDW state stabilized by the NN Coulomb repulsion. The superconductivity coexisting with a CDW order observed in YBa₂Cu₃O_7-δ [S. Kr\"amer and M. Mehring, Phys. Rev. Lett. 83, 396 (1999)] together with the superconductivity of Pr_2-xCeₓCuO_4-y [M. Brinkmann, H. Bach, and K. Westerholt, Physica C 292, 104 (1997)] may be important examples of this pairing mechanism.