Dynamics of the Distorted Diamond Chain

TL;DR

This paper investigates the dynamics of the distorted diamond chain model, analyzing excitation spectra and phase transitions using numerical methods, and discusses its relevance to the material azurite, with implications for neutron scattering experiments.

Contribution

It provides detailed numerical analysis of the excitation spectra and phase transitions in the distorted diamond chain, clarifying the magnetic interactions relevant to azurite.

Findings

Excitation spectra characterized for different phases.

Phase transition behavior analyzed across the SF-TD boundary.

Relevance to azurite confirmed, refuting some previous ferromagnetic coupling claims.

Abstract

We present results on the dynamics of the distorted diamond chain, S=1/2 dimers alternating with single spins 1/2 and exchange couplings $J_1$ and $J_3$ in between. The dynamics in the spin fluid (SF) and tetramer-dimer (TD) phases is investigated numerically by exact diagonalisation for up to 24 spins. Representative excitation spectra are presented, both for zero magnetic field and in the 1/3 plateau phase and the relevant parameters are determined across the phase diagram. The behavior across the SF-TD phase transition line is discussed for the specific heat and for excitation spectra. The relevance of the distorted diamond chain model for the material Cu$_3$(CO$_3$)$_2$(OH)$_2$ (azurite) is discussed with particular emphasis on inelastic neutron scattering experiments, a recent suggestion of one possibly ferromagnetic coupling constant is not confirmed.