Valley polarization is among the most critical attributes of atomically thin materials. However, increasing contrast from monolayer transition metal dichalcogenides (TMDs) has so far been challenging. In this work, a large degree of circular polarization up to 45% from a monolayer WS₂ is achieved at room temperature by using a single chiral plasmonic nanoparticle. The increased contrast is attributed to the selective enhancement of both the excitation and the emission rate having one particular handedness of the circular polarization, together with accelerated radiative recombination of valley excitons due to the Purcell effect. The experimental results are corroborated by the optical simulation using the finite‐difference time‐domain (FDTD) method. Additionally, the single chiral nanoparticle enables the observation of valley‐polarized luminescence with a linear excitation. The results provide a promising pathway to enhance valley contrast from monolayer TMDs and utilize them for nanophotonic devices.

中文翻译：

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单手性纳米颗粒诱导谷极化增强。

谷极极化是原子薄材料的最关键属性之一。然而，迄今为止，与单层过渡金属二卤化二异氰酸酯（TMD）的对比不断提高。在这项工作中，单层WS ₂的圆偏振度高达45％通过使用单个手性等离子体纳米颗粒，可在室温下获得α。对比度的增加归因于具有圆偏振的一种特殊取向的激发和发射速率的选择性增强，以及由于珀塞尔效应引起的谷激子的加速辐射复合。使用有限差分时域（FDTD）方法进行的光学模拟证实了实验结果。此外，单个手性纳米粒子可通过线性激发观察谷偏光。结果为增强单层TMD的谷底对比度并将其用于纳米光子器件提供了有希望的途径。