Investigation of soliton bound states in the Raman spectrum of pure and doped spin-Peierls chains

TL;DR

This paper explores the formation of soliton bound states in the Raman spectra of spin-Peierls chains, revealing how impurities and lattice effects influence spectral features, with implications for understanding CuGeO3.

Contribution

It introduces a detailed analysis of soliton-antisoliton and soliton-impurity bound states in spin chains using advanced numerical methods, connecting theory with experimental observations.

Findings

Prediction of multiple bulk δ-peaks in pure systems

Identification of low energy lines from impurity doping

Sensitivity of bound state energies to lattice relaxation

Abstract

We investigate the occurrence of singlet bound states in the Raman spectrum of dimerized spin 1/2 chains by Exact Diagonalization and Density Matrix Renormalization Group techniques. We predict that several bulk $\delta$-peaks could be observed in pure systems. Furthermore, we show that new low energy lines arise from non-magnetic impurity doping. These features are interpreted in terms of soliton-antisoliton and soliton-impurity bound states respectively. Energies and spectral weights associated with these bound states are sensitive to lattice relaxation effects. Our results are discussed in the context of the inorganic spin-Peierls compound CuGeO$_3$ and quantitatively compared to recent Raman experiments.