Effects of magnetic anisotropy on spin dynamics of ferromagnetic frustrated chain

TL;DR

This study uses advanced numerical methods to analyze how magnetic anisotropy influences spin excitations and bound states in a frustrated one-dimensional quantum spin chain under magnetic fields.

Contribution

It provides detailed insights into the effects of exchange anisotropy on spin excitation spectra and bound state stabilization in a frustrated J1-J2 XXZ model.

Findings

Longitudinal mode remains gapless in the spin quadrupole regime.

Transverse mode has a gap that increases with anisotropy.

Easy-axis anisotropy stabilizes two-magnon bound states.

Abstract

By exploiting density-matrix renormalization group techniques, we investigate the spin dynamics of a spin-1/2 one-dimensional J1-J2 XXZ model with competing ferromagnetic J1 and antiferromagnetic J2 exchange couplings under applied magnetic fields. Numerical results of spin excitation spectra show that in the field-induced spin quadrupole regime, the longitudinal component has a gapless mode and the transverse component has a gapped mode irrespective of the exchange anisotropy. The excitation gap of the transverse spin excitation increases as the exchange anisotropy increases over the XY-like and Ising-like regions, demonstrating that two-magnon bound states are stabilized due to the easy-axis anisotropy.