Neutron scattering as a probe for unconventional superconducting states

Abstract

We show that in the unconventional pairing state of a superconductor, i.e., the state with nodes in its excitation spectrum, the dynamical structure factor S(q,ω) has anomalous resonance peaks in q space. These resonance peaks are due to quasiparticle scattering between different nodes on the Fermi surface. The symmetry of the order parameter and the Fermi-surface geometry uniquely determine the resonance pattern. Observation of such peaks by neutron scattering will unambiguously determine the symmetry of the superconducting pairing state. Quantitative calculations are carried out in two dimensions to demonstrate this unusual effect. Applications to high-${\mathit{T}}_{\mathit{c}}$ oxide superconductors are discussed.