Deconfined quantum criticality and conformal phase transition in two-dimensional antiferromagnets

Deconfined quantum criticality of two-dimensional SU(2) quantum antiferromagnets featuring a transition from an antiferromagnetically ordered ground state to a so-called valence-bond solid state, is governed by a non-compact CP1 model with a Maxwell term in 2 + 1 space-time dimensions. We introduce a new perspective on deconfined quantum criticality within a field-theoretic framework based on an expansion in powers of epsilon = 4 - d for fixed number N of complex matter fields. We show that in the allegedly weak first-order transition regime, a so-called conformal phase transition leads to a genuine deconfined quantum critical point. In such a transition, the gap vanishes when the critical point is approached from above and diverges when it is approached from below. We also find that the spin stiffness has a universal jump at the critical point. Copyright (C) EPLA, 2013