  We investigate the superconducting transition in a doped antiferromagnet.
Based on the phase string framework of the t-J model, an effective model
describing the phase-coherence transition is obtained and is studied through
duality transformation and renormalization group treatment . We show that such
a topological transition is controlled by spin excitations, with the transition
temperature determined by a characterisitic spin excitation energy. The
existence of an Ising-like long range order of staggered current loops is also
discussed.
