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

TL;DR

This paper analyzes neutron scattering data on YBCO in both normal and superconducting states using a bi-layer model, revealing characteristic peaks and maxima consistent with a d-wave superconducting gap and discussing alternative symmetries.

Contribution

It introduces a bi-layer theoretical framework that accurately describes neutron and NMR data in YBCO, highlighting features of the d-wave superconducting state.

Findings

Peaks at q = (π, π, π) in the superconducting state.

Sharp maxima at twice the gap frequency.

Agreement with experimental neutron scattering data.

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 \omega, q and T. A d-wave superconducting state exhibits peaks at q = ( \pi , \pi , \pi ) and sharp maxima as a function of \omega, at twice the gap frequency. This behavior may have been observed experimentally. The counterpart behavior for other choices of order parameter symmetry is discussed.