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 CuGeO3. 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 quasi–elastic line analogous to experiment. PACS: 75.10.Jm, 75.40.Gb, 78.30.-j Typeset using REVTEX 1