Magnetic phases in the S=1 Shastry-Sutherland model with uniaxial anisotropy

TL;DR

This paper investigates the diverse magnetic phases of an S=1 XXZ model with anisotropy on a Shastry Sutherland lattice, revealing new ground states and quantum phenomena not present in S=1/2 systems, with detailed analysis of their properties.

Contribution

It introduces novel ground state phases for the S=1 model, including quantum paramagnetic and spin supersolid phases, and explains the emergence of magnetization plateaus due to quantum fluctuations.

Findings

Identification of new ground states unique to S=1 spins.

Prediction of smaller fractional plateaus at higher spins.

Demonstration of simultaneous diagonal and off-diagonal long-range order.

Abstract

We explore the field induced magnetic phases of an $S=1$ $XXZ$ model with single-ion anisotropy and large Ising-like anisotropy on a Shastry Sutherland lattice over a wide range of Hamiltonian parameters and applied magnetic field. The multitude of ground state phases are characterized in detail in terms of their thermodynamic properties and the underlying classical (Ising limit) spin arrangements for the plateau phases are identified by calculating the static structure factors. The enlarged local Hilbert space of the $S=1$ spins results in several new ground state phases that are not realized for $S=1/2$ spins. These include the quantum paramagnetic state that is ubiquitous to $S=1$ spins with single ion anisotropy, two different spin supersolid phases (with distinct longitudinal ordering) and a magnetization plateau that arises as a direct descendant of the 1/3 plateau due to quantum fluctuations that are not possible for $S=1/2$ spins. We predict the same mechanism will lead to plateaus at smaller fractions of 1/3 for higher spins. 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 as well as the different longitudinal orderings.