Quantum criticality with emergent symmetry in the extended Shastry-Sutherland model

TL;DR

This study uses advanced tensor network simulations to reveal a continuous quantum phase transition with emergent symmetry in the extended Shastry-Sutherland model, providing insights into the quantum criticality observed in the material SrCu_2(BO_3)_2.

Contribution

It demonstrates the existence of a deconfined quantum critical point with emergent O(4) symmetry in the extended Shastry-Sutherland model, supported by large-scale tensor network simulations.

Findings

Identified a continuous transition with emergent O(4) symmetry.

Mapped a phase diagram showing the same DQCP phenomena along a critical line.

Supports the scenario of a proximate deconfined quantum critical point in SrCu_2(BO_3)_2.

Abstract

Motivated by the novel phenomena observed in the layered material $\rm SrCu_2(BO_3)_2$, the Shastry-Sutherland model (SSM) has been extensively studied as the minimal model for $\rm SrCu_2(BO_3)_2$. However, the nature of its quantum phase transition from the plaquette valence-bond solid (PVBS) to antiferromagnetic (AFM) phase is under fierce debate, posing a challenge to understand the underlying quantum criticality. Via the state-of-the-art tensor network simulations, we study the ground state of the SSM on large-scale size up to $20 \times 20$ sites. We identify the continuous transition nature accompanied by an emergent O(4) symmetry between the PVBS and AFM phase, which strongly suggests a deconfined quantum critical point (DQCP). Furthermore, we map out the phase diagram of an extended SSM that can be continuously tuned to the SSM, which demonstrates the same DQCP phenomena along a whole critical line. Our results indicate a compelling scenario for understanding the origin of the proposed proximate DQCP in recent experiments of $\rm SrCu_2(BO_3)_2$.