Anomalously Suppressed Thermal Conduction by Electron‐Phonon Coupling in Charge‐Density‐Wave Tantalum Disulfide

Abstract

Charge and thermal transport in a crystal is carried by free electrons and phonons (quantized lattice vibration), the two most fundamental quasiparticles. Above the Debye temperature of the crystal, phonon‐mediated thermal conductivity (κL) is typically limited by mutual scattering of phonons, which results in κL decreasing with inverse temperature, whereas free electrons play a negligible role in κL. Here, an unusual case in charge‐density‐wave tantalum disulfide (1T‐TaS2) is reported, in which κL is limited instead by phonon scattering with free electrons, resulting in a temperature‐independent κL. In this system, the conventional phonon–phonon scattering is alleviated by its uniquely structured phonon dispersions, while unusually strong electron‐phonon (e‐ph) coupling arises from its Fermi surface strongly nested at wavevectors in which phonons exhibit Kohn anomalies. The unusual temperature dependence of thermal conduction is found as a consequence of these effects. The finding reveals new physics of thermal conduction, offers a unique platform to probe e‐ph interactions, and provides potential ways to control heat flow in materials with free charge carriers. The temperature‐independent thermal conductivity may also find thermal management application as a special thermal interface material between two systems when the heat conduction between them needs to be maintained at a constant level.

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

“…2d). Similar properties were also found in metallic transition-metal nitrides [56] and the charge-density-wave material 1T-TaS2 [57].…”

Four-phonon and electron–phonon scattering effects on thermal properties in two-dimensional 2H-TaS2

“…Liu et al measured the thermal conduction of 1T-TaS 2 only recently and reported an anomalous suppression caused by strong electron-phonon coupling. 34 Additionally, they reported intriguing near temperature (T )-independent κ ph , which could possibly be related to the indirect evaluation of κ ph , namely by subtract-ing κ e , estimated Wiedemann-Franz law (WFL), from κ total . The WFL gives κ e = LσT, where σ is the electrical conductivity and the Lorenz ratio L is assumed to be the Sommerfeld value L 0 .…”

Computational predictions of quantum thermal transport across nanoscale interfaces

“…64 The real part leads to a renormalization of the phonon frequency while the imaginary part modifies the phonon lifetime by introducing an extra source of phonon scattering and can lead to a reduction of the thermal conductance. Recently, this reduction in phonon transport due to EPI has been both experimentally measured 65,66 and computationally predicted. 67–70…”