PHASES OF THE T-J MODEL FROM VARIATIONAL MONTE-CARLO STUDIES - OCCURRENCE OF TIME-REVERSAL SYMMETRY-BREAKING

We have numerically evaluated the energy of several kinds of wave functions considered to be candidate ground states of the two-dimensional t-J model at various hole densities. We searched a parameter space which includes d-wave and s-wave superconductivity and spin-density-wave ordering as well as the projected Fermi-liquid state. Coexistence of different orderings, such as the s+id state and d-wave spin-density-wave state, were found to be stable states. We find a phase diagram in the density-t/J plane which has coexistence of antiferromagnetism and superconductivity at very low hole concentrations and superconductivity up to rather high values of density about 40%. At intermediate concentrations, the time-reversal symmetry-breaking s+id state is found. © 1990 The American Physical Society.