Tensor network study of the Shastry-Sutherland model with weak interlayer coupling

TL;DR

This study uses advanced tensor network techniques to analyze how weak interlayer coupling affects the phase diagram of the Shastry-Sutherland model, providing insights into the material SrCu$_2$(BO$_3$)$_2$ and its intermediate phase stability.

Contribution

The paper introduces a tensor network approach to incorporate weak interlayer coupling into the Shastry-Sutherland model, revealing the destabilization of the intermediate plaquette phase at lower coupling strengths.

Findings

Intermediate plaquette phase destabilized at J''/J~0.04-0.05

Estimated interlayer coupling in SrCu$_2$(BO$_3$)$_2$ is around 0.027

Tensor network methods effectively model layered frustrated spin systems

Abstract

The layered material SrCu$_2$(BO$_3$)$_2$ has long been studied because of its fascinating physics in a magnetic field and under pressure. Many of its properties are remarkably well described by the Shastry-Sutherland model (SSM) - a two-dimensional frustrated spin system. However, the extent of the intermediate plaquette phase discovered in SrCu$_2$(BO$_3$)$_2$ under pressure is significantly smaller than predicted in theory, which is likely due to the weak interlayer coupling that is present in the material but neglected in the model. Using state-of-the-art tensor network methods we study the SSM with a weak interlayer coupling and show that the intermediate plaquette phase is destabilized already at a smaller value around $J''/J\sim0.04-0.05$ than previously predicted from series expansion. Based on our phase diagram we estimate the effective interlayer coupling in SrCu$_2$(BO$_3$)$_2$ to be around $J''/J\sim0.027$ at ambient pressure.