Thermal transport beyond Fourier, and beyond Boltzmann

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• Michele Simoncelli, Theory and Simulation of Materials (THEOS) and National Centre for Computational Design and Discovery of Novel Materials (MARVEL), École Polytechnique Fédérale de Lausanne, Switzerland
• Wednesday 26 February 2020, 11:30-12:30
• TCM Seminar Room, Cavendish Laboratory.

If you have a question about this talk, please contact Angela Harper.

We explore the atomistic mechanisms of thermal transport in solids, elucidating how current formulations can be extended to enlarge their domain of applicability. First, starting from a density-matrix formalism, we show how the phonon Boltzmann transport equation is missing an off-diagonal tunneling term that becomes dominant in complex or glassy materials. The resulting formalism describes on an equal footing heat conduction in crystals, glasses, and anything in between. In particular, it predicts correctly and in agreement with experiments the opposite trends of thermal conductivity in ordered and disordered systems, and the mixed regime of complex thermoelectrics. Then, we show how the Boltzmann transport equation can be coarse grained into a set of viscous heat equations that describe both Fourier diffusion and heat hydrodynamics, matching the recent discovery of hydrodynamic transport/second sound in graphitic devices.

M. Simoncelli, N. Marzari, and F. Mauri, Nat. Phys. 15, 809 (2019).

M. Simoncelli, N. Marzari, and A. Cepellotti, Phys. Rev. X 10 , 011019 (2020).

This talk is part of the Electronic Structure Discussion Group series.

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