Using electron vortex beams to determine chirality of crystals in transmission electron microscopyстатья
Статья опубликована в высокорейтинговом журнале
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Дата последнего поиска статьи во внешних источниках: 8 декабря 2015 г.
Аннотация:We investigate electron vortex beams elastically scattered on chiral crystals. After deriving a general expression
for the scattering amplitude of a vortex electron, we study its diffraction on point scatterers arranged on a helix.
We derive a relation between the handedness of the helix and the topological charge of the electron vortex on one
hand and the symmetry of the higher-order Laue zones in the diffraction pattern on the other for kinematically
and dynamically scattered electrons.We then extend this to atoms arranged on a helix as found in crystals which
belong to chiral space groups and propose a method to determine the handedness of such crystals by looking at
the symmetry of the diffraction pattern. In contrast to alternativemethods, our technique does not require multiple
scattering, which makes it possible to also investigate extremely thin samples in which multiple scattering is
suppressed. In order to verify the model, elastic scattering simulations are performed, and an experimental
demonstration on Mn2Sb2O7 is given in which we find the sample to belong to the right-handed variant of its
enantiomorphic pair. This demonstrates the usefulness of electron vortex beams to reveal the chirality of crystals
in a transmission electron microscope and provides the required theoretical basis for further developments in this
field.