Spin dynamics of dimerized Heisenberg chains

TL;DR

This study numerically investigates the spin dynamics in dimerized Heisenberg chains, revealing a bound state in the dynamical structure factor for any finite dimerization and analyzing the effects of frustration on spin-wave velocity.

Contribution

It provides the first numerical evidence of a bound state in the dynamical structure factor for dimerized Heisenberg chains and quantifies the influence of frustration on spin-wave velocity.

Findings

Presence of a bound state for any finite dimerization 

Spectral weight of the bound state estimated

Spin-wave velocity renormalized by frustration 

Abstract

We study numerically the dimerized Heisenberg model with frustration appropriate for the quasi-1D spin-Peierls compound CuGeO$_3$. We present evidence for a bound state in the dynamical structure factor for any finite dimerization $\delta$ and estimate the respective spectral weight. For the homogeneous case ($\delta=0$) we show that the spin-wave velocity $v_s$ is renormalized by the n.n.n. frustration term $\alpha$ as $v_s=\pi/2 J(1-b\alpha)$ with $b\approx1.12$