The 'Neutron' Magnetic Resonance in the Underdoped Cuprate Superconductor

We show analytically that the magnetic neutron resonance of nonstoichiometrically doped cuprate is a sharp plasmon excitation of the dominant d-wave band at its two-channel Kondo fixed point. Despite existing throughout the 'normal' state, it becomes detectable when Kondo scattering is reduced strongly below the channel transition temperature. Unlike the one-off approach of the current theory of the neutron resonance as the spin exciton, all data relevant to the resonance as well as other phenomena for the crystal are amenable to explanation in the multichannel Kondo approach.