RVB signatures in the spin dynamics of the square-lattice Heisenberg antiferromagnet

TL;DR

This paper uses an improved Schwinger boson mean field approach to analyze the spin dynamics of the square-lattice Heisenberg antiferromagnet, successfully explaining experimental spectral features and the role of RVB-like components.

Contribution

It introduces a novel mean field triplet excitation model combining local and bond spin flips, enhancing the interpretation of experimental spectra in this system.

Findings

Reproduces low and high energy spectral features of experiments.

Attributes spectral weight depletion at (π,0) to RVB bond excitations.

Validates Schwinger boson theory as effective for dynamic properties.

Abstract

We investigate the spin dynamics of the square-lattice spin-1/2 Heisenberg antiferromagnet by means of an improved mean field Schwinger boson calculation. By identifying both, the long range N\'eel and the RVB-like components of the ground state, we propose an educated guess for the mean field triplet excitation consisting on a linear combination of local and bond spin flips to compute the dynamical structure factor. Our main result is that when this triplet excitation is optimized in such a way that the corresponding sum rule is fulfilled, we recover the low and high energy spectral weight features of the experimental spectrum. In particular, the anomalous spectral weight depletion at $(\pi,0)$ found in recent inelastic neutron scattering experiments can be attributed to the interference of the triplet bond excitations of the RVB component of the ground state. We conclude that the Schwinger boson theory seems to be a good candidate to adequately interpret the dynamic properties of the square-lattice Heisenberg antiferromagnet.