Impact of Electron-Phonon Interaction on Thermal Transport: A Review

Abstract

A thorough understanding of the microscopic picture of heat conduction in solids is critical to a broad range of applications, from thermal management of microelectronics to more efficient thermoelectric materials. The transport properties of phonons, the major microscopic heat carriers in semiconductors and insulators, particularly their scattering mechanisms, have been a central theme in microscale heat conduction research. In the past two decades, significant advancements have been made in computational and experimental efforts to probe phonon-phonon, phononimpurity, and phonon-boundary scattering channels in detail. In contrast, electron-phonon scatterings were long thought to have negligible effects on thermal transport in most materials under ambient conditions. This article reviews the recent progress in first-principles computations and experimental methods that show clear evidence for a strong impact of electron-phonon interaction on phonon transport in a wide variety of technologically relevant solid-state materials.Under thermal equilibrium conditions, electron-phonon interactions can modify the total phonon scattering rates and renormalize the phonon frequency, as determined by the imaginary part and the real part of the phonon self-energy, respectively. Under nonequilibrium transport conditions, electron-phonon interactions can affect the coupled transport of electrons and phonons in the bulk through the "phonon/electron drag" mechanism as well as the interfacial thermal transport. Based on these recent results, we evaluate the potential use of electron-phonon interactions to control thermal transport in solids. We also provide an outlook on future directions of computational and experimental developments.

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“…In a Ge-rich system, Ge vacancies with higher defect formation energy 62 can be suppressed a little with Ge impurity. However, the decreasing vacancies and n H may weaken electron–phonon scattering, 63,64 so the sample with y = 0.04 has larger κ L than A3 ( y = 0), as shown in Fig. S9(f) (ESI†).…”

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“…7 Electrons are the main heat carriers in metals. 7,139 The electron contribution to thermal conductivity is directly related to electrical conductivity via the Wiedemann-Franz law (eqn (1)). 7…”

“…7 Electrons are the main heat carriers in metals. 7,139 The electron contribution to thermal conductivity is directly related to electrical conductivity via the Wiedemann–Franz law (eqn (1)). 7 κ e = σLT where σ is electrical conductivity, L is the Lorentz number, and T is temperature.…”

Tutorial: Characterizing Microscale Energy Transport in Materials with Transient Grating Spectroscopy

“…For example, Zhou et al used a modified TGS with an additional excitation beam to directly measure the impact of electron-phonon interaction on the thermal conductivity of a silicon membrane [68]. The scattering of phonons by free charge carriers was long thought to play a negligible role in phonon thermal transport [69].…”