Staggered flux phase in a model of strongly correlated electrons

We present numerical evidence for the existence of a staggered flux (SF) phase in the half-filled two-leg t-U-V-J ladder, with true long-range order in the countercirculating currents. The density-matrix renormalization-group finite-size scaling approach, generalized to describe complex-valued Hamil-tonians and wave functions, is employed. The SF phase exhibits robust currents at intermediate values of the interaction strength.