Spectral weight contributions of many-particle bound states and continuum

TL;DR

This paper develops high-order cluster expansion methods to calculate spectral weight contributions of multiparticle excitations, including continuum and bound states, in quantum spin chains, with detailed results for a specific material and chain configurations.

Contribution

It introduces a comprehensive 11th order calculation framework for spectral weights of multiparticle states in the alternating Heisenberg chain, including bound states and continuum.

Findings

Detailed spectral weights for two-triplet continuum and bound states at λ=0.27.

Analysis of how spectral weights vary with bond alternation from dimerized to uniform chain.

Application to the material Cu(NO_3)_2.2.5D_2O.

Abstract

Cluster expansion methods are developed for calculating the spectral weight contributions of multiparticle excitations - continuum and bound states - to high orders. A complete 11th order calculation is carried out for the alternating Heisenberg chain. For $\lambda=0.27$, relevant to the material $Cu(NO_3)_2.2.5D_2O$, we present detailed spectral weights for the two-triplet continuum and all bound states. We also examine variation of the relative weights of one and two-particle states with bond alternation from the dimerized to the uniform chain limit.