title: First-order phase transition in easy-plane quantum antiferromagnets.
abstract: Quantum phase transitions in Mott insulators do not fit easily into the Landau-Ginzburg-Wilson paradigm. A recently proposed alternative to it is the so-called deconfined quantum criticality scenario, providing a new paradigm for quantum phase transitions. In this context it has recently been proposed that a second-order phase transition would occur in a two-dimensional spin 1/2 quantum antiferromagnet in the deep easy-plane limit. A check of this conjecture is important for understanding the phase structure of Mott insulators. To this end we have performed large-scale Monte Carlo simulations on an effective gauge theory for this system, including a Berry-phase term that projects out the S=1/2 sector. The result is a first-order phase transition, thus contradicting the conjecture.
authors.affiliation: Department of Physics, Norwegian University of Science and Technology, N-7491 Trondheim, Norway.
authors.forename: S
authors.initials: S
authors.lastname: Kragset
authors.forename: E
authors.initials: E
authors.lastname: Smørgrav
authors.forename: J
authors.initials: J
authors.lastname: Hove
authors.forename: F S
authors.initials: FS
authors.lastname: Nogueira
authors.forename: A
authors.initials: A
authors.lastname: Sudbø