Numerical evidence for SO(5) symmetry and superspin multiplets in the t-J model

In this work, we present numerical results which support SO(5) symmetry as a concept unifying superconductivity and antiferromagnetism in high-tempera ture superconductors. Using exact cluster diagonalization, we verify that t he low-energy states of the t-J model, a widely used microscopic model for high T-c cuprates, from SO(5) symmetry multiplets. Our results show that th e d-wave superconducting ground states away from half-filling are obtained from the higher,pin states at half-filling through SO(5) rotations. The dom inant low-energy resonance in the dynamic spin correlation function corresp onds to a 'pi resonance' in the entire low doping region. The SO(5) symmetr y is robust against the inclusion of longer- range Coulomb repulsion and ne xt-nearest-neighbor hopping. (C) 1998 Elsevier Science Ltd. All rights rese rved.