Giant twist-angle dependence of thermal conductivity in bilayer graphene originating from strong interlayer coupling

TL;DR

This study reveals that the thermal conductivity of bilayer graphene can be significantly modulated by twist angle and interlayer coupling, achieving up to 78% reduction through engineered interface interactions.

Contribution

It demonstrates that enhancing interlayer coupling in twisted bilayer graphene dramatically amplifies the twist-angle effect on phonon transport, which was previously considered negligible.

Findings

Thermal conductivity can be increased or decreased by adjusting interlayer coupling and twist angle.

A maximum reduction of 78% in thermal conductivity was achieved with strong interlayer coupling.

The mechanism involves phonon transport modulation based on phonon scattering and localization.

Abstract

Recently, the twist-angle effect on 2D van der Walls (vdW) materials, such as bilayer graphene, has attracted great attention. Many novel electronic, magnetic and even optical properties induced by such effect have been discovered. However, the twist-angle effect on phononic property is not so remarkable. By investigating the thermal conductivity of twist bilayer graphene (TBG), here we reveal that the trivial twist-angle effect on phononic property observed in previous studies is owing to the non-localization nature of phonons. This characteristic makes phonons hardly trapped by the weak interlayer potentials induced by the twist-angle dependent Moir\'e pattern. We propose that the twist-angle effect can be effectively enhanced by increasing the interface coupling. In use of a sandwich structure composed of h-BN and TBG, we demonstrate that the thermal conductivity of TBG can be either significantly increased or dramatically decreased, under the synergistic modulation of interlayer coupling strength and twist angle. Particularly, the twist-angle effect can lead to a nontrivial reduction of thermal conductivity up to 78% when a strong interlayer coupling is applied. The reduction is several times larger than that observed in the freestanding TBG where the reduction is attributed to the twist-angle dependent phonon scatterings induced by the edge phonons. The underlying mechanism for the giant twist-angle dependence of thermal conductivity is further revealed on the basis of phonon transport theory. Our findings provide a platform for achieving efficient twist-angle modulation on phonon transport property of vdW materials.