Berlin 2024 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 28: Focus Session: Heat transport at the nanoscale: theory meets experiment

HL 28.2: Invited Talk

Wednesday, March 20, 2024, 10:00–10:30, EW 203

Hybrid crystal-glass heat conduction and radiative effects in disordered solids — •Michele Simoncelli — Theory of Condensed Matter Group of the Cavendish Laboratory, University of Cambridge

At ordinary temperatures, crystals and glasses exhibit opposite thermal conductivities upon heating: decreasing in the former and increasing in the latter. At extreme temperatures, instead, experiments in crystalline and glassy polar dielectrics show a qualitatively similar strong enhancement in their conductivities, which departs from predictions obtained using state-of-the-art heat-conduction theories. Here, we employ and extend the Wigner formulation of thermal transport to shed light on the microscopic physics determining heat transfer in crystals and glasses over a broad temperature range. First, we show that at ordinary temperatures, the magnitude and trend of the conductivity can be engineered through the degree of disorder in the atomistic bond topology, geometry, or composition of a solid, allowing for the emergence of hybrid crystal-glass conductivity trends. Second, we extend the Wigner formulation to account for phonon-photon couplings; relying on such framework, we show from first principles that the conductivity enhancement in polar dielectrics at extreme temperatures originates from an interplay between conductive and radiative heat transfer and is regulated by atomistic disorder.

Keywords: disordered solids; heat conduction; alloys; light-matter interaction; anharmonicity