Twist-Dependent Anisotropic Thermal Conductivity in Homogeneous MoS2 Stacks

Abstract

Thermal transport property of homogeneous twisted molybdenum disulfide (MoS2) is investigated using non-equilibrium molecular dynamics simulations with the state-of-art force fields. The simulation results demonstrate that the cross-plane thermal conductivity strongly depends on the interfacial twist angle, while it has only a minor effect on the in-plane thermal conductivity, exhibiting a highly anisotropic nature. A frequency-decomposed phonon analysis showed that the cross-plane and in-plane thermal conductivity of MoS2 are dominated by the phonons with frequencies below 12.5 THz and 7.5 THz, respectively. As the interfacial twist angle increases, these low-frequency phonons significantly attenuate the phonon transport across the interface, leading to impeded cross-plane thermal transport. However, the in-plane phonon transport is almost unaffected, which allows for maintaining high in-plane thermal conductivity. Furthermore, our study revealed a strong size dependence for both cross-plane and in-plane thermal conductivities due to the influence of low-frequency phonons in MoS2. The maximum thermal conductivity anisotropy ratio is estimated as ∼400 for twisted MoS2 from our simulation, which is in the same order of magnitude as recent experimental results (∼900). Our study highlights the potential of twist engineering as a tool for tailoring the thermal transport properties of layered materials.