Generation and coherent control of terahertz acoustic phonons in superlattices of perovskite oxides

Abstract

We utilized transmission-type pump–probe technique to investigate coherent acoustic phonons in the superlattices of perovskite oxides such as SrIrO _3 /SrTiO _3 and SrRuO _3 /SrTiO _3 . Because the films in the superlattices are of high-quality and their thicknesses are only several monolayers, quasi-monochromatic acoustic phonons with THz frequency have been achieved. By investigating the propagation of coherent acoustic phonons in the superlattices with different epitaxial periods, the phonon mean free paths of SrTiO _3 were studied in the frequency range between 0.5 THz and 1 THz. We further demonstrated coherent control to amplify or cease the THz coherent acoustic phonon oscillations in the superlattices. By controlling the delay of two pulses for shining the superlattices, the amplitude and phase of the THz coherent acoustic phonons were manipulated. According to the measurements of time-domain Brillouin scatterings, we found the optoacoustic conversion efficiency of SrIrO _3 outperforms that of SrRuO _3 for generating acoustic phonons.

Keywords

• picosecond ultrasonics
• coherent acoustic phonons
• perovskite oxides
• pump–probe
• STO