NUMERICAL EVIDENCE FOR SO(5) SYMMETRY AND SUPERSPIN MULTIPLETS IN THE2-DIMENSIONAL T-J MODEL

In this work, we present numerical results which support SO(5) symmetr y as a concept unifying superconductivity and antiferromagnetism in th e high-temperature superconductors. Using exact cluster diagonalizatio n we verify that low-energy states of the t-J Model, a widely used mic roscopic model for the high-ir, cuprates, form SO(5) symmetry multiple ts. Our results show that the d-wave superconducting ground states awa y from half-filling are obtained from the higher-spin states at half-f illing through SO(5) rotations. The SO(5) symmetry is found to be robu st against the inclusion of longer-ranged Coulomb repulsion and next-n earest-neighbor hopping.