Field-induced decay dynamics in square-lattice antiferromagnet

TL;DR

This paper investigates how magnetic fields affect the decay dynamics of excitations in a square-lattice antiferromagnet, developing a self-consistent theory to regularize singularities and analyze different spin values.

Contribution

It introduces a self-consistent approximation for S >= 1 that removes singularities in decay spectra of the square-lattice Heisenberg antiferromagnet under magnetic fields.

Findings

Regularized magnon decay rates for S=1 and S=5/2.

Analysis of dynamical structure factor in applied magnetic fields.

Identification of decay thresholds and spectral features.

Abstract

Dynamical properties of the square-lattice Heisenberg antiferromagnet in applied magnetic field are studied for arbitrary value S of the spin. Above the threshold field for two-particle decays, the standard spin-wave theory yields singular corrections to the excitation spectrum with logarithmic divergences for certain momenta. We develop a self-consistent approximation applicable for S >= 1, which avoids such singularities and provides regularized magnon decay rates. Results for the dynamical structure factor obtained in this approach are presented for S = 1 and S = 5/2.