Atomistic Defect Makes a Phase Plate for the Generation and High-Angular Splitting of Electron Vortex Beams

Area of Science:

• Solid-state physics
• Materials science
• Electron microscopy

Background:

• Topological defects in solids, such as edge dislocations in antiferromagnetic NiO, can exhibit unique properties not found in their parent materials.
• These defects, characterized by 2π phase winding, can break translational symmetry and lead to emergent phenomena like ferromagnetism.

Purpose of the Study:

• To investigate the interaction between topological defects in NiO and high-energy electron beams.
• To explore the potential of these defects to induce topological orders.
• To develop a novel method for generating electron vortex beams.

Main Methods:

• Utilizing a coherent electron nanobeam in a scanning transmission electron microscope (STEM).
• Recording far-field transmitted patterns as the beam traverses edge dislocation cores in [001] NiO.
• Employing ptychographic techniques to recover phase information and reveal topological phase vortices.

Main Results:

• Observed unique evolution of ⟨020⟩ Bragg disk amplitude patterns, resembling an annular solar eclipse.
• Successfully recovered phase information, revealing topological phase vortices in diffracted electron beams.
• Demonstrated the conversion of electron plane waves to electron vortex beams via atomic topological defects.

Conclusions:

• Atomic topological defects can transform electron wave functions, generating electron vortex beams.
• This method offers a new route for fabricating phase plates capable of producing electron vortex beams with significantly enhanced angular separation.
• The technique facilitates high-resolution, high-efficiency magnetic circular dichroism spectroscopy, advancing the study of symmetry breaking and magnetic properties at the atomic scale.