Stability of the superconducting $d_{x^2-y^2}$ phase in high-$T_{\mathrm{c}}$ superconductors with respect to the intersite Coulomb repulsion of holes at oxygen

It has been shown that, because of the two-orbital character of the subsystem of holes located at oxygen sites and the spatial separation of this subsystem from that of spins at copper ions, the superconducting phase in high-$T_{\mathrm{c}}$ superconductors is stable with respect to the strong Coulomb repulsion of holes located at nearestneighbor oxygen sites if the order parameter has the $d_{x^2-y^2}$ symmetry. This effect is due to the symmetry characteristics of the Coulomb potential, owing to which the equation determining the Cooper pairing in the $d_{x^2-y^2}$ channel does not include this potential.