Three-magnon bound states in exactly rung-dimerized spin ladders

TL;DR

This paper derives exact three-magnon bound states in nonintegrable rung-dimerized spin ladders using Bethe Ansatz and conjectures a dispersion law for larger bound states, revealing complex phase boundary behaviors.

Contribution

It provides the first exact solutions for three-magnon bound states in nonintegrable spin ladders and proposes a conjecture for the dispersion law of larger bound states.

Findings

Exact three-magnon bound states obtained for all total spin sectors.

Conjecture of a dispersion law for m-magnon bound states with m>3.

Behavior of the rung-triplet density may be smooth or abrupt at phase boundary.

Abstract

Three magnon bound states in all total spin sectors of general nonintegrable exactly rung-dimerized spin ladder are obtained by Bethe Ansatz. Basing on this result a dispersion law for $m$-magnon ($m>3$) bound states is conjectured. It is suggested that (depending on correlations between coupling constants) a behavior of the gas parameter (density of rung-triplets) on the boundary of the rung-dimerized phase may either be smooth or have a leap.