Tunning lattice thermal conductivity of bilayer and trilayer molybdenum disulfide thermoelectric materials through twist angles

Abstract

Exploring approaches to reduce lattice thermal conductivity is effective to improve the performance of molybdenum disulfide thermoelectric materials, and tuning lattice thermal conductivity via twist angles attracts increasing attention. However, few studies focused on the effects of twist angle on lattice thermal conductivity of molybdenum disulfide thermoelectric materials, particularly, the coupling effects of two twist angles on lattice thermal conductivity of tri-layer molybdenum disulfide. In this work, the effects of twist angles on lattice thermal conductivity of twisted bilayer and trilayer molybdenum disulfide were investigated by molecular dynamics simulation. Phonon dispersion was calculated through density functional theory to provide a deeper understanding of thermal conduction. The results indicated that for the twisted bilayer sample, the relationship between thermal conductivity and twist angle exhibits “W-shaped”, and the minimum thermal conductivity can be obtained with the twist angle of 15° The phonon analyses indicated that the twist angle has a significant effect on ZA branches, and the effects of the twist angle on group velocities and phonon lifetime of LA and TA branches contribute to the change of thermal conductivity. As for the twisted tri-layer sample, the minimum thermal conductivity can be obtained when the sum of two twist angles is an odd multiple of 15°, which is recommended for thermoelectric materials design.