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 (κ L) is typically limited by mutual scattering of phonons, which results in κ L decreasing with inverse temperature, whereas free electrons play a negligible role in κ L. Here, an unusual case in charge‐density‐wave tantalum disulfide (1T‐TaS2) is reported, in which κ L is limited instead by phonon scattering with free electrons, resulting in a temperature‐independent κ L. 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.
Highlights
Charge and thermal transport in a crystal is carried by free electrons and phonons, the two most fundamental quasiparticles
The Debye temperature of the crystal, phonon-mediated thermal conductivity 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
In metallic systems with very high charge carrier densities, the e-ph scattering could rise to levels that considerably reduce κL, but the measured total thermal conductivity κ = κe + κL would be dominated by the contribution of κe instead
Summary
The unusual temperature-independent thermal conductivity results fundamentally from a nested Fermi surface interplaying with uniquely structured phonon dispersions These conditions could be met in metallic compounds with large cation/anion mass ratios and signatures of strong e-ph coupling such as superconductivity and CDWs. As high density of charge carriers can be introduced by a gate field via either electrostatics or fieldinduced insulator to metal transition,[11,28] the effect reveals a potential way to electrically and locally tune thermal conduction of solids for nonlinear thermal devices.[29,30] New exotic physics of 1T-TaS2, such as quantum spin liquid state,[31] may need to be invoked as possible additional heat carriers. We further state that the honeycomb domain walls network of topological excitations in NCCDW phase identified recently[33] may provide new phonon modes for heat conduction in 1T-TaS2
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
