Pi excitation of the t-J model

Abstract

In this paper, we present analytical and numerical calculations of the [] resonance in the t-J model. We show in detail how the [] resonance in the particle-particle channel couples to the dynamical spin correlation function in a superconducting state. The contribution of the [] resonance to the spin excitation spectrum can be estimated from general model-independent sum rules, and it agrees with our detailed calculations. The results are in overall agreement with the exact diagonalization studies of the t-J model. Earlier calculations predicted the correct doping dependence of the neutron resonance peak in the YBa2Cu3O6 x superconductor, and in this paper detailed energy and momentum dependence of the spin correlation function is presented. The micro- scopic equations of motion obtained within current formalism agree with that of the SO 5 nonlinear [] model, where the [] resonance is interpreted as a pseudo-Goldstone mode of the spontaneous SO 5 symmetry breaking.