Comparative study of Higgs transition in one-component and two-component   lattice superconductor models
  Using Monte Carlo simulations, we study a Higgs transition in several three-dimensional lattice realizations of the noncompact CP$^1$ model (NCCP$^1$), a gauge theory with two complex matter fields with SU(2) invariance. By comparing with a one-component theory, which is well understood and has continuous transition in the inverted XY universality class, we argue that the two-component case also has continuous Higgs transition with a larger correlation length exponent (i.e., it is ``more continuous''). The transition can become first order in the vicinity of a new ``Molecular'' phase, which occurs in one of our models, but is continuous in a wide range of parameters away from this phase. The situation is significantly clarified by studying a model where the Molecular phase is entirely absent, and a wide regime with a continuous transition can be readily established. The two-component theory is also an effective description of the hedgehog-suppressed O(3) universality, and results are relevant for the recently discussed ``deconfined quantum criticality'' scenario for the continuous Valence Bond Solid to Neel quantum phase transition. 
Olexei I. Motrunich and Ashvin Vishwanath