From Magnons to the Resonance Peak: Spin Dynamics in High-T_C Superconducting Cuprates by Inelastic Neutron Scattering

Abstract

The spin dynamics of high temperature superconductors measured by inelastic neutron scattering is reviewed. The spin susceptibility evolves a lot with increasing doping from the undoped insulating state to the overdoped metallic state. In the superconducting state, a strong magnetic resonance peak occurs in the spin excitation spectrum whose energy is proportional to the superconducting temperature. In underdoped and optimally doped regimes, normal state antiferromagnetic fluctuations are observed, proving the existence of strong electronic correlations in cuprates. They are characterized by a spin pseudo-gap. In contrast, these dynamical spin correlations vanish in overdoped samples.