Raman scattering from frustrated quantum spin chains

Magnetic Raman scattering from a frustrated spin-1/2 Heisenberg chain is considered with a focus on the uniform phase of the spin-Peierls compound CuGeO${}_3$. The Raman intensity is analyzed in terms of a Loudon-Fleury scattering process using a spinless-fermion mean-field theory developed for the frustrated spin chain. A comparison to experimental data is presented and the frustration and temperature dependence is studied. In good agreement with observed spectra a broad inelastic four-spinon continuum is found at low temperatures above the spin-Peierls transition. At high temperatures the intensity develops a quasielastic line analogous to experiment.