Four-phonon and electron-phonon scattering effects on thermal properties in two-dimensional 2H-TaS.

Thermal transport characteristics of monolayer trigonal prismatic tantalum disulfide (2H-TaS) are investigated using first-principles calculations combined with the Boltzmann transport equation. Due to a large acoustic-optical phonon gap of 1.85 THz, the four-phonon (4ph) scattering significantly reduces the room-temperature phononic thermal conductivity (). With the further inclusion of phonon-electron scattering, reduces to 1.78 W mK. Nevertheless, the total thermal conductivity () of 7.82 W mK is dominated by the electronic thermal conductivity () of 6.04 W mK. Due to the electron-phonon coupling, differs from the typical estimation based on the Wiedemann-Franz law with a constant Sommerfeld value. This work provides new insights into the physical mechanisms for thermal transport in metallic 2D systems with strong anharmonic and electron-phonon coupling effects. The phonon scattering beyond three-phonon (3ph) scattering and even are typically overlooked in computations, and the constant Sommerfeld value is widely used for separating and from the experimental thermal conductivity. These conclusions have implications for both the computational and experimental measurements of the thermal properties of transition metal dichalcogenides.