D-wave bond order (${\Delta }_x=-{\Delta }_y,{\Delta }_{\mathbf{k}}\propto \cos (k_{x}a)-\cos (k_{y}a)$)

For nearest-neighbor spin-singlet pairing on a square lattice, opposite signs of the pairing amplitude on the two bond directions give the displayed momentum-dependent superconducting gap function. It changes sign under a quarter-turn and has nodes on the zone diagonals. This sign structure is distinct from a nonnegative gap whose magnitude is merely anisotropic. A real pure $d_{x^2-y^2}$ pattern does not by itself require broken time reversal.