We synthesize sub-THz longitudinal quasi-monochromatic acoustic phonons in a SrTiO3 single crystal using a SrRuO3/SrTiO3 superlattice as an optical-acoustic transducer. The generated acoustic phonon spectrum is determined using ultrafast X-ray diffraction. The analysis of the generated phonon spectrum in the time domain reveals a k-vector dependent phonon lifetime. It is observed that even at sub-THz frequencies the phonon lifetime agrees with the 1/ω2 power law known from Akhiezer's model for hyper sound attenuation. The observed shift of the synthesized spectrum to the higher q is discussed in the framework of non-linear effects appearing due to the high amplitude of the synthesized phonons.
@article{arxiv.1303.5643,
title = {Direct time domain sampling of sub-THz coherent acoustic phonon spectra in SrTiO$_3$ using ultrafast X-ray diffraction},
author = {Roman Shayduk and Marc Herzog and André Bojahr and Daniel Schick and Peter Gaal and Wolfram Leitenberger and Hengameh Navirian and Mathias Sander and Jevgenij Goldshteyn and Ionela Vrejoiu and Matias Bargheer},
journal= {arXiv preprint arXiv:1303.5643},
year = {2013}
}