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On the electron vortex beam wavefunction within a crystal

Mendis, B.G.

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Abstract

Electron vortex beams are distorted by scattering within a crystal, so that the wavefunction can effectively be decomposed into many vortex components. Using a Bloch wave approach equations are derived for vortex beam decomposition at any given depth and with respect to any frame of reference. In the kinematic limit (small specimen thickness) scattering largely takes place at the neighbouring atom columns with a local phase change of π/2 rad. When viewed along the beam propagation direction only one vortex component is present at the specimen entrance surface (i.e. the ‘free space’ vortex in vacuum), but at larger depths the probe is in a mixed state due to Bragg scattering. Simulations show that there is no direct correlation between vortex components and the 〈Lz〉 pendellösung, i.e. at a given depth probes with relatively constant 〈Lz〉 can be in a more mixed state compared to those with more rapidly varying 〈Lz〉. This suggests that minimising oscillations in the 〈Lz〉 pendellösung by probe channelling is not the only criterion for generating a strong electron energy loss magnetic circular dichroism (EMCD) signal.

Citation

Mendis, B. (2015). On the electron vortex beam wavefunction within a crystal. Ultramicroscopy, 157, 1-11. https://doi.org/10.1016/j.ultramic.2015.05.004

Journal Article Type Article
Acceptance Date May 4, 2015
Publication Date Oct 1, 2015
Deposit Date Jun 12, 2015
Publicly Available Date Mar 28, 2024
Journal Ultramicroscopy
Print ISSN 0304-3991
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 157
Pages 1-11
DOI https://doi.org/10.1016/j.ultramic.2015.05.004
Keywords Electron vortex beams, Electron energy loss magnetic circular dichroism (EMCD), Bloch waves.

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Copyright Statement
NOTICE: this is the author’s version of a work that was accepted for publication in Ultramicroscopy. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Ultramicroscopy, 157, October 2015, 10.1016/j.ultramic.2015.05.004.





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