Prof. Eun-Gook Moon (KAIST, Physics Department, Korea)
"Exotic Z2 Symmetry Breaking Transitions in 2D Correlated Systems"
The Landau theory of phase transitions is one of the backbones in critical phenomena at non-zero temperatures. With a Z2 symmetry, the theory predicts the Ising universality class. Recent experiments in strongly correlated systems, however, report intriguing possibilities beyond the Landau theory. Here, we uncover an exotic universality class of a Z2 symmetry breaking transition. It is shown that either fractionalization of discrete symmetry order parameters or topological properties may realize the exotic class. In addition to novel critical exponents, we find that the onset of an order parameter may be super-linear in contrast to the sub-linear onset of the Ising class. We argue that a super-linear onset of a Z2 order parameter without breaking a bigger symmetry is evidence of exotic phenomena, and our results are applied to recent experiments in pseudo-gap transitions.