Dynamics and Instabilities of the Shastry-Sutherland Model

TL;DR

This paper investigates the excitation spectrum and phase transitions in the Shastry-Sutherland model using an unbiased variational method, revealing multiple instabilities and order parameters in the system.

Contribution

It introduces a variational approach that works in the thermodynamic limit to identify susceptibilities and instabilities in the Shastry-Sutherland model.

Findings

Identified four different instabilities: antiferro spin nematic, plaquette spin nematic, stripe magnetic order, and plaquette order.

Revealed the nature of phase transitions in the model.

Confirmed some previously reported phases and discovered new potential orderings.

Abstract

We study the excitation spectrum in the dimer phase of the Shastry-Sutherland model by using an unbiased variational method that works in the thermodynamic limit. The method outputs dynamical correlation functions in all possible channels. This output is exploited to identify the order parameters with the highest susceptibility (single or multitriplon condensation in a specific channel) upon approaching a quantum phase transition in the magnetic field versus the $J'/J$ phase diagram. We find four different instabilities: antiferro spin nematic, plaquette spin nematic, stripe magnetic order, and plaquette order, two of which have been reported in previous studies.