Quantum Destruction of Spiral Order in Two Dimensional Frustrated Magnets

TL;DR

This paper investigates how quantum fluctuations and topological defects influence the destruction of spiral magnetic order in two-dimensional frustrated antiferromagnets, revealing a transition to valence-bond solid phases and potential deconfined quantum criticality.

Contribution

It introduces a theory for vortex proliferation-induced phase transition in spiral magnets, linking topological defects to valence-bond solid formation and deconfined quantum critical points.

Findings

Proliferation of Z2 vortices leads to valence-bond solid order.

Disorder of spiral phase can result in a Landau-forbidden quantum critical point.

Develops a general framework for vortex-driven phase transitions in frustrated magnets.

Abstract

We study the fate of spin-1/2 spiral-ordered two-dimensional quantum antiferromagnets that are disordered by quantum fluctuations. A crucial role is played by the topological point defects of the spiral phase, which are known to have a Z2 character. Previous works established that a nontrivial quantum spin-liquid phase results when the spiral is disordered without proliferating the Z2 vortices. Here, we show that when the spiral is disordered by proliferating and condensing these vortices, valence-bond solid ordering occurs due to quantum Berry phase effects. We develop a general theory for this latter phase transition and apply it to a lattice model. This transition potentially provides a new example of a Landau-forbidden deconfined quantum critical point.