Anyonic plaquette flux excitations on the toric code lattice
In Z₂ gauge theory (toric code), visons are gauge-flux excitations that live on plaquettes where the plaquette operator B_p = −1. They are created in pairs by a string of spin-flips. Visons are anyons: braiding an e-particle (vertex excitation) around a vison acquires a phase of −1. In the deconfined phase (h small), visons cost finite energy; in the confined phase (h large), they condense and topological order is lost.