Quantum Criticality with Emergent Symmetry in the Extended Shastry-Sutherland Model

Area of Science:

• Condensed Matter Physics
• Quantum Materials
• Quantum Critical Phenomena

Background:

• The Shastry-Sutherland model (SSM) is a minimal model for the layered material SrCu$_{2}$(BO$_{3}$)$_{2}$, exhibiting novel quantum phenomena.
• Understanding the quantum phase transition in the SSM, particularly between the plaquette valence-bond solid and antiferromagnetic phases, is crucial for comprehending quantum criticality.
• Previous studies have debated the nature of this transition, highlighting challenges in theoretical and experimental investigations.

Purpose of the Study:

• To investigate the ground state properties of the Shastry-Sutherland model on large-scale systems.
• To elucidate the nature of the quantum phase transition within the SSM.
• To explore the phase diagram of an extended SSM and its relation to deconfined quantum critical points (DQCPs).

Main Methods:

• Utilized state-of-the-art tensor network simulations.
• Studied the ground state of the SSM on large system sizes, up to 20x20 sites.
• Mapped out the phase diagram of an extended SSM.

Main Results:

• Identified a continuous quantum phase transition between the plaquette valence-bond solid and antiferromagnetic phases.
• Discovered an emergent O(4) symmetry at the critical point, strongly indicating a deconfined quantum critical point (DQCP).
• Demonstrated DQCP phenomena along a critical line in the extended SSM phase diagram.

Conclusions:

• The findings provide strong evidence for a DQCP in the Shastry-Sutherland model.
• This research offers a compelling theoretical scenario to explain the proximate DQCP observed in recent experiments on SrCu$_{2}$(BO$_{3}$)$_{2}$.
• The study advances the understanding of quantum criticality in frustrated magnetic systems.