Phonon-induced magnon Raman scattering in high Tc cuprates

Abstract

The anomalous line shapes of the Raman spectra of undoped high T c cuprates are analyzed. In order to describe peak structures near 3 J and 4 J in the two-magnon B 1 g Raman spectra, the phonon contribution to the Raman spectra are explored based on the spin wave theory in a two-dimensional Heisenberg antiferromagnet. We have derived the magnon-phonon Hamiltonian from the modulated exchange interaction by the lattice vibrations, and evaluated the Raman spectral function due to the lowest order magnon-phonon-magnon scattering. It is found that the magnon-phonon-magnon scattering gives rise to a phonon-induced magnon peak near 4 J, in good agreement with experiments.