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TT: Fachverband Tiefe Temperaturen
TT 42: 2D Materials III: Electronic Structure (joint session O/TT)
TT 42.10: Talk
Wednesday, March 20, 2024, 12:45–13:00, MA 005
Ultrafast Electron Diffuse Scattering as a Tool for Studying Phonon Transport: Phonon Hydrodynamics and Second Sound Oscillations — •Laurenz Kremeyer1, Tristan Britt1, Bradley Siwick1,2, and Samuel Huberman3 — 1Department for Physics, McGill University, Montreal, Canada — 2Department for Chemistry, McGill University, Montreal, Canada — 3Department of Chemical Engineering, McGill University, Montreal, Canada
Hydrodynamic phonon transport phenomena, like second sound, have been observed in liquid Helium more than 50 years ago. More recently second sound has been observed in graphite at over 200 K using transient thermal grating techniques[1]. In this work we explore the signatures of second sound in ultrafast electron diffuse scattering (UEDS) patterns. We use density functional theory and solve the Boltzmann transport equation to determine time-resolved non-equilibrium phonon populations and subsequently calculate one-phonon structure factors and diffuse scattering patterns to simulate experimental data covering the regimes of ballistic, diffusive, and hydrodynamic phonon transport. For systems like graphite, UEDS is capable of extracting time-dependent phonon occupancies across the entire Brillouin zone [2] and ultimately lead to a more fundamental understanding of the hydrodynamic phonon transport regime.
[1] Ding et al. Nat. Comm. 13 285 (2022)
[2] René de Cotret et al. Phys. Rev. B. 100 214115 (2019)
Keywords: electron diffraction; phonon hydrodynamics; ultrafast electron diffuse scattering; second sound; heat transport