Long-lived phonons.

Abstract

We have demonstrated that long-lived transverse acoustic phonons exist, and that they can be observed as a product of three-particle anharmonic decay of polaritons in GaP. The long-lived phonons are found in a strongly dispersive region of the Brillouin zone and possess a frequency of \ensuremath{\sim}118 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ and a lifetime of 66.5\ifmmode\pm\else\textpm\fi{}5 ns.