Nanoscale Valley Modulation by Surface Plasmon Interference

Exploiting excitons in 2-dimensional (2D) materials has attracted the attention of the community to develop improved photoelectronic devices. Previous reports are based on direct excitation where the out-of-plane illumination projects a uniform single-mode light spot. However, because of the optical diffraction limit, the minimal spot size is a few micrometers, inhibiting the precise manipulation and control of excitons at the nanoscale level. Herein, we introduced the in-plane coherent surface plasmonic interference (SPI) field to excite and modulate excitons remotely. Compared to the out-of-plane light, a uniform in-plane SPI suggests a more compact spatial volume and an abundance of mode selections for a single or an array of device modulation. Our results not only build up a fundamental platform for operating and encoding the exciton states at the nanoscale level but also provide a new avenue toward all-optical integrated valleytronic chips for future quantum computation and information applications.

利用二维（2D）材料中的激子开发更优异的光电子器件，已受到学界的广泛关注。此前的相关研究均基于直接激发方案：采用面外照明投射均匀单模光斑。然而受光学衍射极限限制，最小光斑尺寸仅为数微米，这阻碍了纳米尺度下激子的精准操控与调控。在此工作中，我们引入面内相干表面等离子体激元干涉（SPI）场，以实现激子的远程激发与调制。相较于面外照明光束，均匀面内SPI场具有更紧凑的空间体积，且可为单器件或器件阵列的调制提供丰富的模式选择。本研究不仅为纳米尺度下激子态的操控与编码构建了基础平台，同时也为面向未来量子计算与信息应用的全光集成谷电子芯片开辟了新的研究路径。