Département de génie physique, Polytechnique Montréal, Montréal, Québec, H3C 3A7, Canada.
Département de physique & Regroupement Québécois sur les Matériaux de Pointe (RQMP), Université de Montréal, Montréal, Québec, H2V 0B3, Canada.
Nat Commun. 2023 Jul 11;14(1):4098. doi: 10.1038/s41467-023-39809-3.
The hyperbolic dispersion relation of phonon-polaritons (PhPols) in anisotropic van der Waals materials provides high-momentum states, directional propagation, subdiffractional confinement, large optical density of states, and enhanced light-matter interactions. In this work, we use Raman spectroscopy in the convenient backscattering configuration to probe PhPol in GaSe, a 2D material presenting two hyperbolic regions separated by a double reststrahlen band. By varying the incidence angle, dispersion relations are revealed for samples with thicknesses between 200 and 750 nm. Raman spectra simulations confirm the observation of one surface and two extraordinary guided polaritons and match the evolution of PhPol frequency as a function of vertical confinement. GaSe appears to provide relatively low propagation losses and supports confinement factors matching or exceeding those reported for other 2D materials. Resonant excitation close to the 1s exciton singularly exalts the scattering efficiency of PhPols, providing enhanced scattering signals and means to probe the coupling of PhPols to other solid-state excitations.
在各向异性范德瓦尔斯材料中，声子极化激元（PhPol）的双曲色散关系提供了高动量态、定向传播、亚衍射限制、大光学态密度和增强的光物质相互作用。在这项工作中，我们使用 Raman 光谱在方便的背散射配置中探测 GaSe 中的 PhPol，GaSe 是一种呈现两个双曲区的二维材料，这两个双曲区由双远红外带隔开。通过改变入射角，我们揭示了厚度在 200 到 750nm 之间的样品的色散关系。Raman 光谱模拟证实了对一个表面和两个非寻常导极化激元的观察，并与 PhPol 频率随垂直限制的演化相匹配。GaSe 似乎提供了相对较低的传播损耗，并支持与其他二维材料报告的相当或更高的限制因子。接近 1s 激子的共振激发奇异地提高了 PhPol 的散射效率，提供了增强的散射信号，并为探测 PhPol 与其他固态激发的耦合提供了手段。
