Observation of three-magnon light scattering in CuGeO_3

Abstract

Temperature and magnetic field dependent polarized Brillouin spectra of CuGeO_3 are reported. In addition to a bound singlet state at 30 cm^{-1}, a new feature has been observed at 18 cm^{-1}. This feature is interpreted in terms of a novel three-magnon light scattering process between excited triplet states.

RevTeX, 4 pages, 3 eps figures, Phys. Rev. Lett. in press