The Union Jack model: a quantum spin model with frustration on the square lattice

TL;DR

This paper introduces the Union Jack quantum spin model on the square lattice, analyzing its phases using spin-wave theory, revealing N{é}el order at low frustration, a canted phase at high frustration, and discussing potential spin-liquid phases.

Contribution

It presents a novel frustrated quantum spin model and analyzes its phase diagram using spin-wave theory, highlighting phase transitions and the possibility of spin-liquid states.

Findings

Néel order at low frustration levels

Canted phase emergence at high frustration

Discussion of potential intermediate spin-liquid phase

Abstract

A new quantum spin model with frustration, the `Union Jack' model on the square lattice, is analyzed using spin-wave theory. For small values of the frustrating coupling $\alpha$, the system is N{\' e}el ordered as usual, while for large $\alpha$ the frustration is found to induce a canted phase. The possibility of an intermediate spin-liquid phase is discussed.