Modulation of thermal conductivity in graphene semi-encapsulated monolayer 2D β-bismuthene through twist angle engineering

Abstract

Two-dimensional (2D) β-bismuthene, characterized by intrinsically low thermal conductivity and excellent optoelectronic properties, is a promising material for thermoelectric and nanoelectronic applications. Nevertheless, its thermal transport behavior in heterostructures remains insufficiently understood. In this work, we investigate the twist-angle-dependent thermal transport in graphene semi-encapsulated monolayer β-bismuthene using non-equilibrium molecular dynamics simulations. The results show that graphene encapsulation substantially enhances the in-plane thermal conductivity of β-bismuthene layer in graphene-semi-encapsulated heterostructures, with a maximum increase of 180.90 % compared to pristine monolayer β-bismuthene. As the twist angle increases from 0° to 10.89°, the thermal conductivity decreases monotonically by up to 13.80 %. Meanwhile, the interface thermal resistance increases from 2.03 × 10⁻⁷ to 2.19 × 10⁻⁷ Km²W⁻¹, reflecting weakened interlayer coupling. Phonon density of states and transmission spectra analyses indicate that low-frequency phonon softening and phonon localization are responsible for the reduction in thermal conductivity. Stress analysis further reveals that higher twist angles induce stronger interfacial stress concentration, with the average atomic stress increasing by ∼12.30 %, thereby enhancing phonon scattering. Potential energy surface calculations show that the interfacial energy variation decreases significantly from 0.62 meV to 0.13 meV with increasing twist angle, confirming the progressive weakening of vdW interfacial coupling. Overall, this study provides microscopic insights into thermal transport modulation in graphene/β-bismuthene heterostructures and offers guidance for designing advanced thermal management materials based on two-dimensional β-bismuthene.