  We show that the order-disorder phase transition in the three state Potts
ferromagnet on a square lattice is driven by a coupled proliferation of
vortices and domain walls. Raising the vortex core energy above a certain value
decouples the proliferation and splits the transition into two. The phase
between the two transitions exhibits an emergent U(1) symmetry and quasi long
range order. Lowering the core energy also splits the order-disorder transition
but the proliferation does not decouple and a vortex lattice appears as the
intermediate phase.
