SURFACE BRILLOUIN-SCATTERING FROM LAYERED METALS AND SEMIMETALS

The authors report the observation of surface Brillouin spectra from seven layered transition metal dichalcogenide metals and semimetals. Spectra of all materials clearly exhibit narrow peaks corresponding to thermally excited surface Rayleigh waves which scatter light via the recently proposed surface ripple mechanism. Materials of lower opacity exhibit additional spectral features attributable to scattering from bulk transverse and longitudinal phonons via the elasto-optic mechanism. Peak frequencies, intensities and scattering selection rules are compared with theoretical predictions.