Theory of the coupling of quantum-critical fluctuations to fermions andd-wave superconductivity in cuprates

The quantum-critical fluctuations of the time-reversal breaking order parameter which is observed in the pseudogap regime of the cuprates are shown to couple to the lattice equivalent of the local angular momentum of the fermions. Such a coupling favors scattering of fermions through angles close to ±π/2 which is unambiguously shown to promote d-wave pairing. The right order of magnitude of Tc and the zero temperature gap Δ/Tc are calculated using the same fluctuations which give the anomalous normal state properties for dopings near the quantum-critical value.