室温下狄拉克流体巨可调热扩散率的观测
Observation of giant and tuneable thermal diffusivity of Dirac fluid at room temperature
摘要：
导电材料通常表现出扩散或弹道电荷传输。然而，当电子-电子相互作用占主导地位时，出现具有粘性电荷流的流体动力学状态（1-13）。更严格的条件最终会产生量子临界的狄拉克流体状态，其中电子热可以比电荷更有效地流动（14-22）。在这里，我们观察石墨烯中的热传输在扩散和流体动力学制度，并报告一个可控的过渡到狄拉克流体制度在室温下，使用载流子温度和载流子密度作为控制旋钮。我们介绍了时空热电显微镜技术与飞秒时间和纳米空间分辨率，它允许跟踪电子热扩散。在扩散状态下，我们发现热扩散率为$\sim$ 2,000 cm $^2$ /s，与电荷传输一致。值得注意的是，在动量弛豫之前的流体动力学时间窗口期间，我们观察到对应于高达70，000 cm $^2$ /Vs的巨大扩散率的热扩散，这表明狄拉克流体。这些结果是有希望的应用，如纳米热管理。
英文摘要：
Conducting materials typically exhibit either diffusive or ballistic charge transport. However, when electron-electron interactions dominate, a hydrodynamic regime with viscous charge flow emerges (1-13). More stringent conditions eventually yield a quantum-critical Dirac-fluid regime, where electronic heat can flow more efficiently than charge (14-22). Here we observe heat transport in graphene in the diffusive and hydrodynamic regimes, and report a controllable transition to the Dirac-fluid regime at room temperature, using carrier temperature and carrier density as control knobs. We introduce the technique of spatiotemporal thermoelectric microscopy with femtosecond temporal and nanometre spatial resolution, which allows for tracking electronic heat spreading. In the diffusive regime, we find a thermal diffusivity of $\sim$2,000 cm$^2$/s, consistent with charge transport. Remarkably, during the hydrodynamic time window before momentum relaxation, we observe heat spreading corresponding to a giant diffusivity up to 70,000 cm$^2$/Vs, indicative of a Dirac fluid. These results are promising for applications such as nanoscale thermal management.
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