Magnetization Plateaus in the Two-dimensional S = 1/2 Heisenberg Model with a 3$\times$3 Checkerboard Structure

TL;DR

This paper explores the phase diagram and spin dynamics of a 2D S=1/2 Heisenberg model with a 3x3 checkerboard structure under magnetic field, revealing detailed properties of magnetization plateaus and phase transitions.

Contribution

It provides the first detailed analysis of magnetization plateaus, phase transitions, and spin excitations in this specific checkerboard lattice model using quantum Monte Carlo and spin wave theory.

Findings

Identification of multiple magnetization plateau phases at 1/9, 3/9, 5/9, 7/9

Determination of phase transition points in the 3D XY universality class

Characterization of spin excitation spectra in different phases

Abstract

We investigate the S=1/2 antiferromagnetic Heisenberg model with a 3$\times$3 checkerboard lattice structure in a longitudinal magnetic field. By using the stochastic series expansion quantum Monte Carlo (SSE-QMC) method, we obtain the properties of the non-plateau XY phase, 1/9, 3/9, 5/9, 7/9 magnetization plateau phases, and fully polarized phase. Then, we determine the precise phase transition critical points belonging to the 3D XY universality class through finite-size scaling. Moreover, we study the longitudinal and transverse dynamic spin structure factors of this model in different phases. For the non-plateau XY phase, the energy spectra present a gap between the low-energy gapless branch and the high-energy part under the competition of magnetic field and interaction. The gapless branch can be described by the spin wave theory in the canted antiferromagnetic phase of the effective "block spin" model. In the magnetization plateau phase, we identify that the excitation arises from localized disturbances within the sublattice, which are capable of spreading in momentum space. This study offers theoretical insights and interpretations for the characteristics of the ground state and the inelastic neutron scattering spectrum in two-dimensional quantum magnetic materials. Specifically, it focuses on materials with a checkerboard unit cell structure and odd-spin configurations under the influence of a longitudinal magnetic field.