Department of Physics, Columbia University, New York, NY, USA.
Department of Physics, University of California San Diego, San Diego, CA, USA.
Science. 2023 Feb 10;379(6632):555-557. doi: 10.1126/science.adf1065. Epub 2023 Feb 9.
We visualized negative refraction of phonon polaritons, which occurs at the interface between two natural crystals. The polaritons-hybrids of infrared photons and lattice vibrations-form collimated rays that display negative refraction when passing through a planar interface between the two hyperbolic van der Waals materials: molybdenum oxide (MoO) and isotopically pure hexagonal boron nitride (hBN). At a special frequency ω, these rays can circulate along closed diamond-shaped trajectories. We have shown that polariton eigenmodes display regions of both positive and negative dispersion interrupted by multiple gaps that result from polaritonic-level repulsion and strong coupling.
我们观察到了声子极化激元的负折射，这种现象发生在两种天然晶体的界面处。极化激元是红外光子和晶格振动的混合体，当它们穿过两种双曲范德华材料（氧化钼（MoO）和同位素纯六方氮化硼（hBN））之间的平面界面时，会形成准直光线，表现出负折射。在一个特殊的频率 ω 下，这些光线可以沿着封闭的菱形轨迹循环。我们已经证明，极化激元本征模式显示出正色散和负色散的区域，它们被极化激元能级排斥和强耦合产生的多个间隙所打断。
