Assessing phonon coherence using spectroscopy

As a fundamental physical quantity of thermal phonons, temporal coherence participates in a broad range of thermal and phononic processes, while a clear methodology for the measurement of phonon coherence is still lacking. In this paper, we derive a theoretical model for the experimental exploration of phonon coherence based on spectroscopy, which is then validated by comparing Brillouin light scattering data and direct molecular dynamic simulations of confined modes in nanostructures. The proposed model highlights that confined modes exhibit a pronounced wavelike behavior characterized by a higher ratio of coherence time to lifetime. The dependence of phonon coherence on system size is also demonstrated from the spectroscopy data. The proposed theory allows for reassessing the data of conventional spectroscopy to yield coherence times, which are essential for the understanding and the estimation of phonon characteristics and heat transport in solids in general.

Automated summary

In this paper, a theoretical model for exploring phonon coherence based on spectroscopy is proposed and validated using Brillouin light scattering data and molecular dynamic simulations. The model shows that confined modes exhibit wavelike behavior with a higher ratio of coherence time to lifetime. The spectroscopy data also demonstrates the dependence of phonon coherence on system size. The proposed model allows for reassessing conventional spectroscopy data to obtain coherence times, which are crucial for understanding and estimating phonon characteristics and heat transport in solids.