EVANESCENT FIELD RAMAN-SCATTERING BY ROTON-TYPE EXCITATIONS

Evanescent field Raman scattering of light is proposed as a method for probing roton-type peculiarities of the excitation spectrum of 2D ele ctron gas in a strong magnetic field. These peculiarities are essentia l for the modern theories of the fractional quantum Hall effect. We pr edict the magnetoroton contribution to bc comparable to the intensity, measured in the conventional backscattering geometry. This method may also be applied to 3D samples, exhibiting the roton-type spectrum of quasiparticles. Particularly, in the familiar case of rotons in liquid He-4, we show that the contribution of evanescent field Raman scatter ing by rotons is expected to be comparable to the Mandelstam-Brillouin contribution.