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Mechanical Detection and Imaging of Hyperbolic Phonon Polaritons in Hexagonal Boron Nitride
ACS Nano ( IF 15.8 ) Pub Date : 2017-09-05 00:00:00 , DOI: 10.1021/acsnano.7b02323
Antonio Ambrosio 1 , Luis A. Jauregui , Siyuan Dai 2 , Kundan Chaudhary , Michele Tamagnone , Michael M. Fogler 2 , Dimitri N. Basov 2, 3 , Federico Capasso , Philip Kim , William L. Wilson
Affiliation  

Mid-infrared nanoimaging and spectroscopy of two-dimensional (2D) materials have been limited so far to scattering-type scanning near-field optical microscopy (s-SNOM) experiments, where light from the sample is scattered by a metallic-coated atomic force microscope (AFM) tip interacting with the material at the nanoscale. These experiments have recently allowed imaging of plasmon polaritons in graphene as well as hyperbolic phonon polaritons in hexagonal boron nitride (hBN). Here we show that the high mechanical sensitivity of an AFM cantilever can be exploited for imaging hyperbolic phonon polaritons in hBN. In our imaging process, the lattice vibrations of hBN micrometer-sized flakes are locally enhanced by the launched phonon polaritons. These enhanced vibrations are coupled to the AFM tip in contact with the sample surface and recorded during scanning. Imaging resolution of Δ/20 is shown (Δ being the polaritonic fringes’ separation distance), comparable to the best resolution in s-SNOM. Importantly, this detection mechanism is free from light background, and it is in fact the first photonless detection of phonon polaritons.

中文翻译:

六方氮化硼中双曲线声子极化子的机械检测与成像

到目前为止,二维(2D)材料的中红外纳米成像和光谱学仅限于散射型扫描近场光学显微镜(s-SNOM)实验,在该实验中,来自样品的光被金属涂层的原子力散射显微镜(AFM)尖端在纳米级与材料相互作用。这些实验最近允许对石墨烯中的等离激元极化子以及六方氮化硼(hBN)中的双曲声子极化子进行成像。在这里,我们表明可以利用AFM悬臂的高机械灵敏度来成像hBN中的双曲声子极化子。在我们的成像过程中,发射的声子极化子会局部增强hBN微米级薄片的晶格振动。这些增强的振动耦合到与样品表面接触的AFM尖端,并在扫描过程中记录下来。图中显示了Δ/ 20的成像分辨率(Δ是极化子条纹的分离距离),与s-SNOM中的最佳分辨率相当。重要的是,这种检测机制不受光背景的影响,实际上这是声子极化子的第一个无光子检测。
更新日期:2017-09-06
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