Plaquette Singlet Transition, Magnetic Barocaloric Effect, and Spin Supersolidity in the Shastry-Sutherland Model

TL;DR

This study uses advanced tensor network methods to explore phase transitions, magnetic cooling effects, and spin supersolidity in the Shastry-Sutherland model, providing insights relevant to experimental frustrated quantum magnets.

Contribution

It reveals a first-order plaquette-singlet transition, a critical endpoint, magnetic barocaloric effects, and a quantum phase transition to a spin supersolid phase in the SS model.

Findings

Identification of a first-order PS to dimer transition with a critical endpoint.

Discovery of magnetic barocaloric effects in the supercritical regime.

Observation of a PS to spin supersolid quantum phase transition.

Abstract

Inspired by recent experimental measurements [Guo \textit{et al.}, Phys. Rev. Lett.~\textbf{124}, 206602 (2020); Jim\'enez \textit{et al.}, Nature \textbf{592}, 370 (2021)] on frustrated quantum magnet SrCu$_2$(BO$_3$)$_2$ under combined pressure and magnetic fields, we study the related spin-$1/2$ Shastry-Sutherland (SS) model using state-of-the-art tensor network methods. By calculating thermodynamics, correlations and susceptibilities, we find, in zero magnetic field, not only a line of first-order plaquette-singlet (PS) to dimer-singlet phase transition ending with a critical point, but also signatures of the ordered PS transition with its critical endpoint terminating on this first-order line. Moreover, we uncover prominent magnetic barocaloric responses, a novel type of quantum correlation induced cooling effect, in the strongly fluctuating supercritical regime. Under finite fields, we identify a quantum phase transition from the PS phase to the spin supersolid phase that breaks simultaneously lattice translational and spin rotational symmetries. The present findings on the SS model are accessible in current experiments and would shed new light on exotic critical and supercritical phenomena in archetypal frustrated quantum magnets.