Phase structure and phase transitions in a three dimensional SU(2) superconductor

TL;DR

This study investigates the phase diagram and transitions of a 3D SU(2) superconductor model, revealing a sequence of two phase transitions with an intermediate O(3) phase, using large-scale Monte Carlo simulations.

Contribution

It provides the first detailed analysis of the phase structure in this model, identifying a bicritical point and resolving bimodal energy distributions at low couplings.

Findings

Discovery of a two-transition sequence with an intermediate O(3) phase.

New estimate for the bicritical point location.

Resolution of bimodal energy histograms at low coupling strengths.

Abstract

We study the three dimensional SU(2)-symmetric noncompact CP1 model, with two charged matter fields coupled minimally to a noncompact Abelian gauge-field. The phase diagram and the nature of the phase transitions in this model have attracted much interest after it was proposed to describe an unusual continuous transition associated with deconfinement of spinons. Previously, it has been demonstrated for various two-component gauge theories that weakly first-order transitions may appear as continuous ones of a new universality class in simulations of relatively large, but finite systems. We have performed Monte-Carlo calculations on substantially larger systems sizes than those in previous works. We find that in some area of the phase diagram where at finite sizes one gets signatures consistent with a single first-order transition, in fact there is a sequence of two phase transitions with an O(3) paired phase sandwiched in between. We report (i) a new estimate for the location of a bicritical point and (ii) the first resolution of bimodal distributions in energy histograms at relatively low coupling strengths. We perform a flowgram analysis of the direct transition line with rescaling of the linear system size in order to obtain a data collapse. The data collapses up to coupling constants where we find bimodal distributions in energy histograms.