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

ABSTRACT: 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 hexagonal boron nitride, a representative van der Waals material. The boron nitride spectra depend on the flake thickness and on the distance of the electron beam to the flake edges. To explain these observations, we developed a classical response theory that describes the interaction of fast electrons wi

SUBMITTER: Govyadinov AA 

PROVIDER: S-EPMC5522439 | biostudies-literature | 2017 Jul

REPOSITORIES: biostudies-literature