Transport Waves as Crystal Excitations

Abstract

We introduce the concept of transport waves by showing that the linearized Boltzmann transport equation admits excitations in the form of waves that have well defined dispersion relations and decay times. Crucially, these waves do not represent single-particle excitations, but are collective excitations of the equilibrium distribution functions. We study in detail the case of thermal transport, where relaxons are found in the long-wavelength limit, and second sound is reinterpreted as the excitation of one or several temperature waves at finite frequencies. Graphene is studied numerically, finding decay times of the order of microseconds. The derivation, obtained by a spectral representation of the Boltzmann equation, holds in principle for any crystal or semiclassical transport theory and is particularly relevant when transport takes place in the hydrodynamic regime.

References in corpus (2)

• Quantum ESPRESSO: a modular and open-source software project for quantum simulations of materials
• Thermal transport in crystals as a kinetic theory of relaxons

Cited by in corpus (12)

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• Phonon hydrodynamics in crystalline GeTe at low temperature
• Thermal dynamics and electronic temperature waves in layered correlated materials
• Analysis of nonlocal phonon thermal conductivity simulations showing the ballistic to diffusive crossover
• Effect of characteristic size on the collective phonon transport in crystalline GeTe
• Theory of Transient Heat Conduction
• Vortices and backflow in hydrodynamic heat transport
• Non-local thermal transport modeling using the thermal distributor
• Thermal transport in crystals: from the quantum Dyson equation to mesoscopic phonon hydrodynamics