Deconfined pseudocriticality in a model spin-1 quantum antiferromagnet

TL;DR

This paper investigates a spin-1 quantum antiferromagnet model, providing evidence for deconfined pseudocriticality in a Ne9el to cVBS transition through large-scale QMC simulations, challenging the traditional continuous transition paradigm.

Contribution

The study offers a microscopic model realization of deconfined pseudocriticality in spin-1 systems, extending the understanding of quantum critical points beyond spin-b4 models.

Findings

Evidence of a single critical point with high-quality data collapse

Signs of pseudocriticality rather than true criticality in the transition

Observation of $U(1)$-symmetric cVBS histograms and non-diverging order parameter histograms

Abstract

Berry phase interference arguments that underlie the theory of deconfined quantum criticality (DQC) for spin-$\frac{1}{2}$ antiferromagnets have also been invoked to allow for continuous transitions in spin-1 magnets including a N\'eel to (columnar) valence bond solid (cVBS) transition. We provide a microscopic model realization of this transition on the square lattice consisting of Heisenberg exchange ($J_H$) and biquadratic exchange ($J_B$) that favor a N\'eel phase, and a designed $Q$-term ($Q_B$) interaction which favors a cVBS through large-scale quantum Monte Carlo (QMC) simulations. For $J_H=0$, this model is equivalent to the $SU(3)$ $JQ$ model with a N\'eel-cVBS transition that has been argued to be DQC through QMC. Upon turning on $J_H$ which brings down the symmetry to $SU(2)$, we find multiple signatures -- a single critical point, high quality collapse of correlation ratios and order parameters, "$U(1)$-symmetric" cVBS histograms and lack of double-peak in order parameter histograms for largest sizes studied near the critical point -- that are highly suggestive of a continuous transition scenario. However, Binder analysis finds negative dips that grow sub-extensively that we interpret as these transitions rather being pseudocritical. This along with recent results on spin-$\frac{1}{2}$ models suggests that deconfined pseudocriticality is the more generic scenario.