Room-temperature strong coupling between plasmonic nanocavities and monolayer semiconductors is a prominent path towards efficient, integrated light-matter interactions. However, designing such systems is challenging due to the nontrivial dependence of the strong coupling on various properties of the cavity and emitter, as well as the subwavelength scale of the interaction. In this work, we develop a methodology for obtaining hybrid nanostructures consisting of plasmonic metasurfaces coupled to atomically thin WS2 layers, exhibiting extreme values of Rabi splitting, by inverse design of the near-field plasmonic response. Contrary to common measures such as the quality factor or the mode volume, our method relies on an overlap-integral-based metric. We experimentally measure large values of Rabi splitting for our nanoantenna designs, while providing theoretically optimal configurations for several additional types of nanostructures. Our results open a path to maximizing light-matter interactions in integrated platforms, for classical and quantum-optical applications.
Observation of giant and tuneable thermal diffusivity of Dirac fluid at room temperature
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。
