论文标题
尺寸交叉对范德华材料中声子传输的影响：石墨和石墨烯的案例研究
Impact of dimensional crossover on phonon transport in van der Waals materials: a case study of graphite and graphene
论文作者
论文摘要
使用第一原理建模，我们通过逐渐将石墨中的原子层拉开以形成石墨烯时，研究了声子在从3D到2D上进行分层/范德华材料的演变，反之亦然。重点放在确定可能与其他分层材料共享的影响热导率的功能。发现高电导率的石墨$κ$低于石墨烯，这主要是由于由范德华偶联驱动的声子分散的变化。具体而言，随着原子层的距离更近，石墨烯中的声学弯曲声子形成了石墨中低能的光弯曲声子，该石墨中具有较低的面积速度，密度的状态和声子占用，从而减少了$κ$。从2D到3D过渡时，在其他范德华材料中可能会发生类似的分散变化和对导热率的影响。我们的发现还表明，石墨烯中的选择规则减少了声子 - 音纸散射并有助于其大$κ$，随着原子层被汇集在一起形成石墨。虽然选择规则并不严格适用于石墨，但实际上显示了类似的散射行为，部分原因是较弱的层间耦合。这表明范德华（Van der Waals）以散装3D形式的材料比其他非上层散装材料的声子散射率较低。
Using first-principles modeling, we investigate how phonon transport evolves in layered/van der Waals materials when going from 3D to 2D, or vice versa, by gradually pulling apart the atomic layers in graphite to form graphene. Focus is placed on identifying the features impacting thermal conductivity that are likely shared with other layered materials. The thermal conductivity $κ$ of graphite is found to be lower than that of graphene mainly due to changes in the phonon dispersion driven by van der Waals coupling. Specifically, as the atomic layers are brought closer together, the acoustic flexural phonons in graphene form low-energy optical flexural phonons in graphite that possess lower in-plane velocities, density-of-states and phonon occupation, thus reducing $κ$. Similar dispersion changes, and impact on thermal conductivity, can be expected in other van der Waals materials when transitioning from 2D to 3D. Our findings also indicate that the selection rules in graphene, which reduce phonon-phonon scattering and contribute to its large $κ$, effectively hold as the atomic layers are brought together to form graphite. While the selection rules do not strictly apply to graphite, in practice similar scattering behavior is displayed due in part to the weak inter-layer coupling. This suggests that van der Waals materials, in bulk 3D form, may have lower phonon-phonon scattering rates than other non-layered bulk materials.
