Modified Spin Wave Thoery of the Bilayer Square Lattice Frustrated Quantum Heisenberg Antiferromagnet

TL;DR

This paper investigates the ground state phases of a frustrated bilayer quantum antiferromagnet using a modified spin wave approach, revealing transitions between ordered, disordered, and spin liquid phases depending on interlayer coupling and frustration.

Contribution

It introduces a modified spin wave method to analyze the phase diagram of the bilayer square lattice frustrated quantum Heisenberg antiferromagnet, highlighting the nature of disordered phases.

Findings

Weak interlayer coupling yields magnetic order.

Large coupling induces quantum disordered phases.

Strong frustration leads to quantum spin liquid behavior.

Abstract

The ground state of the square lattice bilayer quantum antiferromagnet with nearest and next-nearest neighbour intralayer interaction is studied by means of the modified spin wave method. For weak interlayer coupling, the ground state is found to be always magnetically ordered while the quantum disordered phase appear for large enough interlayer coupling. The properties of the disordered phase vary according to the strength of the frustration. In the regime of weak frustration, the disordered ground state is an almost uncorrelated assembly of interlayer dimers, while in the strongly frustrated regime the quantum spin liquid phase which has considerable N\'eel type short range order appears. The behavior of the sublattice magnetization and spin-spin correlation length in each phase is discussed.