title: Complex critical exponents for percolation transitions in Josephson-junction arrays, antiferromagnets, and interacting bosons.
abstract: We show that the critical behavior of the XY quantum-rotor model undergoing a percolation transition is dramatically affected by its topological Berry phase 2π ρ. In particular, for irrational ρ, its low-energy excitations emerge as spinless fermions with fractal spectrum. As a result, critical properties not captured by the usual Ginzburg-Landau-Wilson description of phase transitions arise, such as complex critical exponents, log-periodic oscillations and dynamically broken scale invariance.
authors.affiliation: Ames Laboratory, Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA.
authors.forename: Rafael M
authors.initials: RM
authors.lastname: Fernandes
authors.forename: Jörg
authors.initials: J
authors.lastname: Schmalian