Columnar antiferromagnetic order and spin supersolid phase on the extended Shastry-Sutherland lattice

TL;DR

This study uses quantum Monte Carlo simulations to explore an extended Shastry-Sutherland model, revealing a spin supersolid phase and magnetic orderings relevant to rare earth tetraborides like ErB4.

Contribution

It demonstrates the stabilization of a spin supersolid phase in an extended model, providing detailed structure factor analysis and guiding experimental searches.

Findings

Columnar antiferromagnetic order at zero field

Extended magnetization plateau at 1/2 saturation

Existence of a spin supersolid phase between phases

Abstract

We use large scale quantum Monte Carlo simulations to study an extended version of the canonical Shastry-Sutherland model -- including additional interactions and exchange anisotropy -- over a wide range of interaction parameters and an applied magnetic field. The model is appropriate for describing the low energy properties of some members of the rare earth tetraborides. Working in the limit of large Ising-like exchange anisotropy, we demonstrate the stabilization of columnar antiferromagnetic order in the ground state at zero field and an extended magnetization plateau at 1/2 the saturation magnetization in the presence of an applied longitudinal magnetic field -- qualitatively similar to experimentally observed low-temperature phases in ErB$_4$. Our results show that for an optimal range of exchange parameters, a spin supersolid ground state is realized over a finite range of applied field between the columnar antiferromagnetic phase and the magnetization plateau. The full momentum dependence of the longitudinal and transverse components of the static structure factor is calculated in the spin supersolid phase to demonstrate the simultaneous existence of diagonal and off-diagonal long-range order. Our results will provide crucial guidance in designing further experiments to search for the interesting spin supersolid phase in ErB$_4$.