Tuning and mapping hybrid polaritons at the nanoscale

本项目旨在研究二维VDW材料中层间相互作用产生的光学性质。通过将前沿纳米技术与纳米尺度分析相结合，我们将最终实现具有纳米尺度限制和低损耗的混合极化子模式，为未来基于光的信息技术的可能应用奠定基础。在二维材料中，极化子可以显着增强光与物质的相互作用。极化子是一种准粒子，它是由电磁波(如光)和物质中携带激发的偶极之间的耦合产生的。-典型的物质激发是自由电子的集体振荡(表面等离子体极化子)、晶格振动(声子极化子)或将电子从价带提升到传导带(激子极化子)。极化子导致电荷传输、化学反应性和局域势的变化，但也可能提供极端的光局域化和增强的电磁态密度。不同2D材料的堆叠使得极化子能够耦合到在激发类型、耦合强度、局域化和传播行为上具有很大程度可调谐的混合模。因此，二维异质结可以用于具有特殊物理性质的按需设计。在这里，我们提出了调谐由单晶银或石墨烯与六方氮化硼(HBN)组成的2D异质结构中的等离子体和声子的混合模。离子束纳米溅射将允许以5 nm的精度修改几何形状，以精确地调整这两个单独的激发以及它们之间的耦合强度。利用低损耗扫描电子显微镜(STEM)和电子能量损失谱(EELS)，可以得到完整的色散关系。混合模式的空间分辨率为&lt；1 nm，能量分辨率为&lt；6 mev，动量分辨率为&lt；0.2 nm-1。用电子束作为脉冲，同时用一个探头激发和探测所选择的模式，将获得前所未有的空间和能量分辨率与飞秒时间分辨率的结合。考虑到制造和分析技术的极高空间分辨率，将在单个样品上实现大参数空间的调查。

This project aims at the investigation of 'optical properties emergingfrom interlayer interactions in 2D vdW materials'. By combiningcutting-edge nanopatterning with nanoscale analysis we will ultimatelyrealize hybrid polaritonic modes with nanoscale confinement and lowlosses for possible applications in light-based future informationtechnology. In two-dimensional (2D) materials light-matter interaction canbe significantly enhanced by polaritons. A polariton is a quasiparticlethat results from coupling between an electro-magnetic wave, such aslight, and a dipole carrying excitation in matter. ‐ Typical matterexcitations are collective oscillations of free electrons (surfaceplasmon polaritons), lattice vibrations (phonon polaritons) or liftingelectrons from the valence to the conduction band (excitonpolaritons). Polaritons lead to changes in charge transport, chemicalreactivity and local potentials but may also provide for extreme lightlocalization and an enhanced density of electromagnetic states.Stacking of different 2D materials enables coupling of polaritons tohybrid modes with a large degree of tunability in the type of excitation,their coupling strength, and their localization and propagationbehaviour. Thereby, 2D heterostructures can serve for on-demanddesign of extraordinary physical properties. Here, we propose to tunehybrid modes of plasmons and phonons in 2D heterostructures fromsingle-crystalline silver or graphene with hexagonal boron nitride(hBN). He ion beam nanopatterning will allow to modify geometrieswith an accuracy <5 nm for the precise adjustment of both, theseparate excitations and the coupling strength between them. Usinglow-loss scanning transmission electron microscopy (STEM) electronenergy-loss spectroscopy (EELS), complete dispersion relations willbe obtained. Hybrid modes will be mapped with a simultaneousspatial resolution of <1 nm, energy resolution of <6 meV, andmomentum resolution of <0.2 nm-1. By using the electron beam as apulse and a probe simultaneously to excite and probe selectedmodes, unprecedented spatial and energy resolution will be combinedwith fs temporal resolution. Given the extremely high spatial resolutionof both, fabrication and analysis techniques, a large parameter spacefor investigation will be realized on a single sample.