Thermal Kharkiv Seminars: "Heat Capacity and Thermal Conductivity of Solids at Low Temperatures"
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Temperature dependence of thermal conductivity in glasses, from wave packets description of heat carriers
prof. Anne Tanguy
Laboratory LaMCoS - Institut National des Sciences Appliquées de Lyon, France
Figure 1. Ballistic and Diffusive contributions to the thermal conductivity as a function of the temperature, for an amorphous material including nano-inclusions with different elastic impedance mismatch.
The unusual shape of vibration modes due to elastic heterogeneities in glasses makes the wave vector not well adapted to describe acoustic excitations such as phonons. The propagation of heat carriers in glasses may however be described in terms of wave packets propagation and diffusion, the latter resulting from scattering processes on disorder. The transition from the ballistic to the diffusive behaviour occurs at the Ioffe-Regel frequency above which the mean-free path of phonons becomes smaller than its wavelength.
In this talk, we involve molecular dynamics simulations to show that this behaviour contributes to explain the saturation and then the Arrhenius behaviour of the Thermal conductivity as a function of the temperature (Fig. 1). We show then that the low temperature behaviour of thermal conductivity in glasses depends also strongly on the amplitude of the excitation [1,2].
[1] . Tanguy, Vibrations and Heat Transfer in Glasses: The Role Played by Disorder , Comptes Rendus de Physique de l'Académie 24 (S1), 73-97 (2023).
[2] P. Desmarchelier, A. Carré, K. Termentzidis and A. Tanguy, Ballistic Heat Transport in Nanocomposite: The Role of the Shape and Interconnection of Nanoinclusions , Nanomaterials , 11, 1982 (2021).
[3] A. Tlili, V. Giordano, Y. Beltukov, P. Desmarchelier, S. Merabia and A. Tanguy, Enhancement and anticipation of the Ioffe-Regel crossover in amorphous / nanocrystalline composites , Nanoscale 11, 21502-21512 (2019).
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