Exotic continuous quantum phase transition between Z2 topological spin liquid and Neel order

TL;DR

This paper proposes a theoretical framework for a continuous quantum phase transition between a Z2 topological spin liquid and Neel order, driven by bound state proliferation, with universal critical exponents computed.

Contribution

It introduces a novel theory for the Z2-Neel transition involving (e, m)-type excitations and predicts emergent correlations, advancing understanding of exotic quantum critical points.

Findings

Universal critical exponents calculated using 1/N expansion.

Prediction of emergent quasi long-range correlations at the transition.

Proposed mechanism involving bound state proliferation of spinon-vison pairs.

Abstract

Recent numerical simulations with different techniques have all suggested the existence of a continuous quantum phase transition between the Z2 topological spin liquid phase and a conventional Neel order. Motivated by these numerical progresses, we propose a candidate theory for such Z2-Neel transition. We first argue on general grounds that, for a SU(2) invariant system, this transition cannot be interpreted as the condensation of spinons in the Z2 spin liquid phase. Then we propose that such Z2-Neel transition is driven by proliferating the bound state of the bosonic spinon and vison excitation of the Z2 spin liquid, i.e. the so called (e, m)-type excitation. Universal critical exponents associated with this exotic transition are computed using 1/N expansion. This theory predicts that at the Z2-Neel transition, there is an emergent quasi long range power law correlation of columnar valence bond solid order parameter.