Impact of optical phonons on the thermal conductivity of monolayer WSe2 due to four-phonon scattering

Abstract

There exists a large debate on the thermal conductivity(TC) of monolayer WSe2. The first-principles method is thus explored to investigate the TC of monolayer WSe2 with and without considering four-phonon scattering(FPS). It is observed that the TC of monolayer WSe2 is 52.49 W/m·K considering only three-phonon scattering(TPS) at 300 K. However, the TC is significantly reduced to 7.74 W/m·K, only 14.75 % of that of TPS considered, when the FPS is involved. Moreover, the optical phonons make negligible contributions to the total TC with TPS; however, their contribution increases to about 20 %, due to the inclusion of the FPS. Additionally, with temperature increasing, the thermal conductivity contribution from three- and four-phonon scattering tends to converge, indicating a diminishing contribution of the higher-order phonon scattering.