Speaker: Wenjie Ji (McMaster University)
Title: Self-dual Higgs transitions: Toric code and beyond
Abstract: In (2+1)d, the transition from a Z_2 gauge theory (toric code phase) to a trivial phase can be driven by the condensation of either the electric (e) or magnetic (m) charge. When the system has a global Z_2 “self-duality” symmetry that exchanges e and m charges, the naive anyon-condensation picture no longer holds since e and m cannot simultaneously condense. Numerical studies, beginning about 17 years ago, have found a continuous transition from the toric code with the Z_2 self-duality symmetry to a trivial phase with the Z_2 spontaneously broken. Since then, it has been a challenge to understand the transition from a field-theory perspective. In this talk, I will provide a field theory that gives a natural mean-field picture of the phase diagram. The theory can be further generalized to a whole series describing analogous transitions involving non-Abelian topological orders, such as the S_3 quantum double.