Thin graphite gets cool fast In nonmetallic solids, heat is transported primarily through crystal vibrations called phonons. These phonons can have wavelike properties under certain conditions, which increases the thermal conductivity of the material. Machida et al. found that making graphite samples thin expands the hydrodynamic regime from cryogenic to room temperatures. The researchers measured an extremely high thermal conductivity in the very thin graphite samples, which may be important for a variety of electronics applications. Science, this issue p. 309 Eight-layer graphite has a room-temperature thermal conductivity higher than that of diamond. 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.

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薄石墨中的声子流体动力学和超高室温热导率

薄石墨快速冷却 在非金属固体中，热量主要通过称为声子的晶体振动传递。这些声子在某些条件下可以具有波状特性，这增加了材料的热导率。町田等人。发现使石墨样品变薄可以将流体动力学范围从低温扩展到室温。研究人员在非常薄的石墨样品中测量了极高的热导率，这对于各种电子应用可能很重要。科学，这个问题 p。309 八层石墨的室温导热系数高于金刚石。碳的同素异形体，例如金刚石和石墨烯，是最好的热导体之一。我们监测了薄石墨中热导率随温度和厚度的变化，并发现了高导电率、厚度和声子流体动力学之间的密切联系。8.5 微米厚石墨的室温面内热导率为每米开尔文 4300 瓦——该值远高于金刚石，略大于同位素纯化石墨烯。变暖增强了整个温度范围内的热扩散率，支持部分流体动力学声子流。我们观察到的导热率随着厚度的减小而增强，这表明声子的面外动量与动量松弛碰撞的分数之间存在相关性。我们认为这是由于石墨中极端的声子色散各向异性。