Quantum spin ladder with dynamic phonons. Bound states of magnons and phonons

TL;DR

This paper investigates how dynamic phonons influence the magnetic excitations in a quantum spin ladder, revealing significant changes in magnon dispersion and the emergence of magnon-phonon bound states.

Contribution

It introduces a novel analysis of magnon-phonon interactions in a two-chain Heisenberg ladder, highlighting the formation of bound states due to dynamic phonons.

Findings

Dynamic phonons alter magnon dispersion and spin structure factor.

A new triplet bound state of magnon and phonon is identified.

Interaction with phonons significantly impacts magnetic excitation spectra.

Abstract

We consider the two-chain Heisenberg ladder with antiferromagnetic interactions. Our approach is based on the description of spin excitations as triplets above a strong-coupling singlet ground state. It is shown that interaction with dynamic phonons drastically changes the dispersion of the elementary triplet excitation (magnon) and the spin structure factor. It is also shown that a new triplet excitation appears in the spectrum: the bound state of a magnon and a phonon.