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

HF Feng and B Liu and ZX Guo, PHYSICAL REVIEW B, 108, L241405 (2023).

DOI: 10.1103/PhysRevB.108.L241405

Recently, the twist-angle effect on two-dimensional van der Waals (vdW) materials, such as bilayer graphene, has attracted great attention. Many novel electronic, magnetic, and even optical properties induced by such effects have been discovered. However, the twist-angle effect on a phononic property is not so remarkable. By investigating the thermal conductivity of twisted bilayer graphene (TBG), we reveal that the trivial twist-angle effect on a phononic property observed in previous studies is owing to the nonlocalization nature of phonons. This characteristic makes phonons hardly trapped by the weak interlayer potentials induced by the twist-angle dependent moire pattern. We propose that the twist-angle effect can be effectively enhanced by increasing the interface coupling. Using a sandwich structure composed of hexagonal boron nitride 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 by up to 78% when a strong interlayer coupling is applied. The reduction is several times larger than that observed in the freestanding TBG originating from the twist-angle dependent phonon scatterings induced by the edge phonons. The underlying mechanism for the giant twist-angle dependent thermal conductivity is further revealed based on phonon transport theory. Our findings provide a platform for achieving efficient twist- angle modulation on the phonon transport property of vdW materials.

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