S. Kragset

First-Order Phase Transition in Easy-Plane Quantum Antiferromagnets

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.

Quantum critical scaling behavior of deconfined spinons

We perform a renormalization group analysis of some important effective field theoretic models for deconfined spinons. We show that deconfined spinons are critical for an isotropic

Instanton correlators and phase transitions in two- and three-dimensional logarithmic plasmas

\mathrm{SU}(N)

Metal-insulator transition in two- and three-dimensional logarithmic plasmas

Heisenberg antiferromagnet, if

Thermal fluctuations of vortex matter in trapped bose-einstein condensates.

N

Effects of boundaries and density inhomogeneity on states of vortex matter in Bose-Einstein condensates at finite temperature

is large enough. We argue that nonperturbatively this result should persist down to

Preemptive vortex-loop proliferation in multicomponent interacting Bose-Einstein condensates

N=2

Preemptive phase-transitions in multicomponent BECs

and provide further evidence for the so-called deconfined quantum criticality scenario. Deconfined spinons are also shown to be critical for the case describing a transition between quantum spin nematic and dimerized phases. On the other hand, the deconfined quantum criticality scenario is shown to fail for a class of easy-plane models. For the cases where deconfined quantum criticality occurs, we calculate the critical exponent

Thermal Fluctuations of Vortex Matter in Trapped Bose-Einstein Condensates

\ensuremath{\eta}

Crossover States of Vortex Matter in Trapped Bose Condensates

for the decay of the two-spin correlation function to first-order in