Evidence for dx2-y2 pairing from nuclear-magnetic-resonance experiments in the superconducting state of YBa2Cu3O7

Abstract

We calculate the electron spin susceptibility for the superconducting state of ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_7$ using a band structure with nearest- and next-nearest-neighbor hopping, a momentum-dependent spin-spin interaction, and a superconducting gap with ${\mathit{d}}_{\mathit{x}}^2$-${\mathit{y}}^2$ symmetry. Our calculated nuclear magnetic relaxation rates and Knight shift agree favorably with experiment. Our work provides further evidence for a ${\mathit{d}}_{\mathit{x}}^2$-${\mathit{y}}^2$ pairing state and demonstrates that antiferromagnetic correlations persist in the superconducting state.