Department of Physics, Gakushuin University, Tokyo 171-8588, Japan.
Laboratoire Physique et Etude de Matériaux (CNRS-Sorbonne Université-ESPCI), PSL Research University, 75005 Paris, France.
Science. 2020 Jan 17;367(6475):309-312. doi: 10.1126/science.aaz8043.
Allotropes of carbon, such as diamond and graphene, are among the best conductors of heat. We monitored the evolution of thermal conductivity in thin graphite as a function of temperature and thickness and found an intimate link between high conductivity, thickness, and phonon hydrodynamics. The room-temperature in-plane thermal conductivity of 8.5-micrometer-thick graphite was 4300 watts per meter-kelvin-a value well above that for diamond and slightly larger than in isotopically purified graphene. Warming enhances thermal diffusivity across a wide temperature range, supporting partially hydrodynamic phonon flow. The enhancement of thermal conductivity that we observed with decreasing thickness points to a correlation between the out-of-plane momentum of phonons and the fraction of momentum-relaxing collisions. We argue that this is due to the extreme phonon dispersion anisotropy in graphite.
碳的同素异形体，如金刚石和石墨烯，是热的最佳导体之一。我们监测了薄石墨的热导率随温度和厚度的变化，发现高导电性、厚度和声子流体力学之间存在密切联系。8.5 微米厚石墨的室温面内热导率为 4300 瓦/米-开尔文-这一数值高于金刚石，略高于同位素纯化石墨烯。升温增强了热扩散，在很宽的温度范围内都支持部分流体动力学声子流。我们观察到厚度减小导致热导率增强，这表明声子的面外动量与动量弛豫碰撞的分数之间存在相关性。我们认为这是由于石墨中声子的极端色散各向异性所致。
