The hybrid combination of two-dimensional (2D) transition metal dichalcogenides (TMDs) and plasmonic materials open up novel means of (ultrafast) optoelectronic applications and manipulation of nanoscale light–matter interaction. However, control of the plasmonic excitations by TMDs themselves has not been investigated. Here, we show that the ultrathin 2D WSe₂ crystallites permit nanoscale spatially controlled coherent excitation of surface plasmon polaritons (SPPs) on smooth Au films. The resulting complex plasmonic interference patterns are recorded with nanoscale resolution in a photoemission electron microscope. Modeling shows good agreement with experiments and further indicates how SPPs can be tailored with high spatiotemporal precision using the shape of the 2D TMDs with thicknesses down to single molecular layers. We demonstrate the use of WSe₂ nanocrystals as 2D optical elements for exploring the ultrafast dynamics of SPPs. Using few-femtosecond laser pulse pairs we excite an SPP at the boundary of a WSe₂ crystal and then have a WSe₂ monolayer wedge act as a delay line inducing a spatially varying phase difference down to the attosecond time range. The observed effects are a natural yet unexplored consequence of high dielectric functional values of TMDs in the visible range that should be considered when designing metal–TMD hybrid devices. As the 2D TMD crystals are stable in air, can be defect free, can be synthesized in many shapes, and are reliably positioned on metal surfaces, using them to excite and steer SPPs adds an interesting alternative in designing hybrid structures for plasmonic control.

中文翻译：

---

使用二维过渡金属二硫属化物相干激发和控制金上的等离子体

二维 (2D) 过渡金属二硫属元素化物 (TMD) 和等离子体材料的混合组合开辟了（超快）光电应用和纳米级光-物质相互作用操纵的新方法。然而，尚未研究 TMD 本身对等离子体激发的控制。在这里，我们展示了超薄 2D WSe ₂微晶允许在光滑的 Au 薄膜上对表面等离子体激元 (SPP) 进行纳米级空间控制相干激发。由此产生的复杂等离子体干涉图案在光电电子显微镜中以纳米级分辨率记录。建模显示出与实验的良好一致性，并进一步表明如何使用厚度低至单分子层的 2D TMD 的形状以高时空精度定制 SPP。我们展示了使用 WSe ₂纳米晶体作为 2D 光学元件来探索 SPP 的超快动力学。使用几飞秒激光脉冲对，我们在 WSe ₂晶体的边界处激发 SPP，然后得到 WSe ₂单层楔作为延迟线，在阿秒时间范围内引起空间变化的相位差。观察到的效应是在设计金属-TMD 混合器件时应考虑的可见光范围内 TMD 的高介电功能值的自然但尚未探索的结果。由于 2D TMD 晶体在空气中稳定，可以无缺陷，可以合成多种形状，并且可靠地定位在金属表面上，使用它们来激发和引导 SPP，为设计用于等离子体控制的混合结构增加了一个有趣的选择。