Abstract
In this work we present our recent results of the ab initio calculations of anharmonic coupling in cubic semiconductors and bismuth. Our results allow us to explain the anomalous behavior of the attenuation of the longitudinal acoustic phonon in GaAs as a function of the phonon energy in the subterahertz domain, which shows a plateau between 0.6 and 1 THz at low temperatures. The plateau is explained by the competition between different phonon-phonon scattering processes such as Herring’s mechanism, which dominates at low frequencies, saturates, and disappears at higher frequencies. We found an excellent agreement between measurements performed by some of us, and new ab initio calculations of third-order anharmonic processes. We predict that the same phenomenon should occur in other cubic semiconductors. In the case of bismuth, we discuss the occurrence of the hydrodynamic heat transport regime at low temperatures, in consistency with the experimental observations. Bismuth is one of the rare materials in which second sound has been experimentally observed. Our calculations predict the occurrence of the Poiseuille phonon flow in Bi between 1.5 K and 3.5 K for sample size of 3.86 mm and 9.06 mm, in consistency with the experimental observations. We will also discuss a Gedanken experiment allowing to assess the occurrence of the hydrodynamic regime in any bulk material.
Highlights
Phonon-phonon interaction manifests itself in a wealth of temperature-induced physical phenomena like melting, thermal transport, and in the increase with temperature of phonon linewidths observed in Raman spectroscopy
Recent experimental measurements on the absorption of subterahertz longitudinal waves made by some of us in gallium arsenide [10] showed that after a steep increase, the attenuation exhibits an unexpected plateau as a function of the excitation frequency in the 700 GHz to 1 THz range
We report on our recent ab initio calculations of third-order anharmonic processes which have shown that the formation of the plateau can be explained by the competition between different phonon-phonon scattering processes such as Herring’s mechanism, which dominates at low frequencies, saturates, and disappears [13]
Summary
Phonon-phonon interaction manifests itself in a wealth of temperature-induced physical phenomena like melting, thermal transport, and in the increase with temperature of phonon linewidths observed in Raman spectroscopy. As temperature increases, anharmonic coupling between phonons increases and gives rise to scattering processes that limit the mean free paths of phonons in general, and of heat-carrying phonons in particular.
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