Theory of Neutron Scattering in the Normal and Superconducting State of YBCO

Abstract

We analyze neutron experiments on $\ybco$ at various stoichiometries in the superconducting state, within the context of a bi-layer theory which yields good agreement with the normal state Cu-NMR and neutron data as a function of ω, q and T. A d-wave superconducting state exhibits peaks at q = ( π, π, π) and sharp maxima as a function of ω, at twice the gap frequency. This behavior may have been observed experimentally. The counterpart behavior for other choices of order parameter symmetry is discussed.