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Observation of second sound in graphite over 200 K.

ABSTRACT: Second sound refers to the phenomenon of heat propagation as temperature waves in the phonon hydrodynamic transport regime. We directly observe second sound in graphite at temperatures of over 200 K using a sub-picosecond transient grating technique. The experimentally determined dispersion relation of the thermal-wave velocity increases with decreasing grating period, consistent with first-principles-based solution of the Peierls-Boltzmann transport equation. Through simulation, we reveal this increase as a result of thermal zero sound-the thermal waves due to ballistic phonons. Our experimental findings are well explained with the interplay among three groups of phonons: ballistic, diffusive, and hydrodynamic phonons. Our ab initio calculations further predict a large isotope effect on the properties of thermal waves and the existence of second sound at room temperature in isotopically pure graphite.

SUBMITTER: Ding Z

PROVIDER: S-EPMC8755757 | biostudies-literature | 2022 Jan

REPOSITORIES: biostudies-literature

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Observation of second sound in graphite over 200 K.

Ding Zhiwei Z Chen Ke K Song Bai B Shin Jungwoo J Maznev Alexei A AA Nelson Keith A KA Chen Gang G

Nature communications 20220112 1

Second sound refers to the phenomenon of heat propagation as temperature waves in the phonon hydrodynamic transport regime. We directly observe second sound in graphite at temperatures of over 200 K using a sub-picosecond transient grating technique. The experimentally determined dispersion relation of the thermal-wave velocity increases with decreasing grating period, consistent with first-principles-based solution of the Peierls-Boltzmann transport equation. Through simulation, we reveal this ...[more]

PMID: 35022394

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