Cryogenic angle-resolved Brillouin–Mandelstam spectroscopy of surface and bulk acoustic phonons in diamond

We used angle-resolved Brillouin–Mandelstam light-scattering spectroscopy to monitor surface and bulk acoustic phonons in diamond along the ⟨100⟩ and ⟨110⟩ crystallographic directions across a temperature range from 10 to 300 K. The frequencies and phase velocities were measured for three types of surface acoustic phonons: Rayleigh waves, shear horizontal waves, and high-frequency pseudo-longitudinal waves. All surface acoustic phonons exhibit weak temperature dependence, with the largest observed coefficient of variation of 2.44% across the examined temperature range. The frequencies of all three types of surface acoustic phonons agree with the theoretical values within the experimental uncertainty. Cryogenic surface-acoustic-phonon data are important for diamond-based quantum sensors, surface acoustic wave devices, and other electronic technologies. Knowledge of surface acoustic phonons can also be used for developing accurate models for thermal transport between interfaces.