Anisotropic in-plane lattice thermal conductivity in bilayer ReS2

TL;DR

This study uses first-principles calculations to reveal that bilayer ReS2 exhibits persistent in-plane thermal conductivity anisotropy influenced by stacking order, with potential implications for device optimization.

Contribution

It provides the first detailed analysis of how stacking order affects thermal transport anisotropy in bilayer ReS2 using DFT methods.

Findings

Anisotropic thermal conductivity ratios are approximately 1.08 and 1.12 for AA and AB stacking.

Anisotropic thermal properties remain stable up to 1000K.

AB stacking shows stronger layer coupling and lower thermal conductivity due to phonon scattering.

Abstract

The significantly weak interlayer coupling strength and puckered structure provide the novel layer-tolerant and anisotropic features in two-dimensional (2D) ReS2. These unique features offer an opportunity to modulate the optoelectronic, vibrational, and transport properties along different lattice directions in ReS2. Here, using first-principles density functional theory (DFT), we investigated the thermal transport properties of ReS2 in AA and AB stacking orders. The anisotopic ratios for lattice thermal conductivities (\k{appa}) are found to be 1.08 and 1.12 for AA and AB stacking, respectively. This anisotropic nature remains intact even at higher temperatures up to 1000K, demonstrating anisotropic robustness. Lower symmetry in AB stacking leads to higher phonon scattering, which results in lower group velocity, smaller phonon lifetime, and thereby lower \k{appa} along both directions as compared to AA stacking. The strong breathing and shear Raman modes in AB stacking indicate stronger layer coupling, further confirming the dominant contribution of acoustic modes towards thermal transport. The findings underscore that the stacking-order-driven preferential heat flow in ReS2 and opens up a new dimension for optimizing device performance.