Probing low-energy hyperbolic polaritons in van der Waals crystals with an electron microscope

  title={Probing low-energy hyperbolic polaritons in van der Waals crystals with an electron microscope},
  author={Alexander A. Govyadinov and Andrea Kone{\vc}n{\'a} and Andrey L. Chuvilin and Sa{\"u}l V{\'e}lez and Irene Dolado and Alexey Yu Nikitin and Sergei Lopatin and F{\`e}lix Casanova and Luis E. Hueso and Javier Aizpurua and Rainer Hillenbrand},
  journal={Nature Communications},
Van der Waals materials exhibit intriguing structural, electronic, and photonic properties. Electron energy loss spectroscopy within scanning transmission electron microscopy allows for nanoscale mapping of such properties. However, its detection is typically limited to energy losses in the eV range—too large for probing low-energy excitations such as phonons or mid-infrared plasmons. Here, we adapt a conventional instrument to probe energy loss down to 100 meV, and map phononic states in… 
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