Abstract
We have observed, for the first time, inelastic neutron scattering from the phonons externally excited in single crystals. We have used ultrasonic transducers (50–200 MHz) for the excitation and neutron spin-echo spectroscopy for observing acoustic phonons. This allowed us to trace evolution of the elastic Bragg intensity I(0) and of the phonon harmonics up to the seventh order as a function of the excitation power. In contrast to the common belief, we have found that in perfect Si ultrasound does not seriously increase I(0), but an apparent increase in the Bragg intensity is entirely due to the onset of inelastic scattering. At the highest power we observed a cross-over to a chaotic phonon behavior. In deformed Si I(0) strongly decreases at a low acoustic power. The same effect could be observed in KBr and graphite crystals where the ultrasonic field made the entire mosaic blocks vibrate.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
