Ultrafast generation and control of an electron vortex beam via chiral plasmonic near fields.

G M Vanacore,I Kaminer,V Grillo,P Biagioni,R J Lamb,G Berruto,F J García De Abajo,H Larocque,F Carbone,E Pomarico,D Mcgrouther,O Reinhardt,E Karimi,I Madan,B Barwick

doi:10.1038/s41563-019-0336-1

Abstract

Vortex-carrying matter waves, such as chiral electron beams, are of significant interest in both applied and fundamental science. Continuous-wave electron vortex beams are commonly prepared via passive phase masks imprinting a transverse phase modulation on the electron's wavefunction. Here, we show that femtosecond chiral plasmonic near fields enable the generation and dynamic control on the ultrafast timescale of an electron vortex beam. The vortex structure of the resulting electron wavepacket is probed in both real and reciprocal space using ultrafast transmission electron microscopy. This method offers a high degree of scalability to small length scales and a highly efficient manipulation of the electron vorticity with attosecond precision. Besides the direct implications in the investigation of nanoscale ultrafast processes in which chirality plays a major role, we further discuss the perspectives of using this technique to shape the wavefunction of charged composite particles, such as protons, and how it can be used to probe their internal structure.

Highlights

The quantum wave nature of both light and matter has enabled several tools to shape them into new wave structures defined by exotic non-trivial spatio-temporal properties [1]
Provided that the modulus of the wave is circularly symmetric, the presence of this term causes the wave to carry orbital angular momentum (OAM), as it effectively becomes an eigenstate of the z component of the OAM operator with eigenvalue mħ, where ħ is the reduced Planck constant
Vortices in electron waves have become increasingly present in modern science, especially in electron microscopy [11,12,13,14]

Summary

Introduction

The quantum wave nature of both light and matter has enabled several tools to shape them into new wave structures defined by exotic non-trivial spatio-temporal properties [1]. The resulting position-dependent interference between the propagating light field and the SPP field gives rise to a spatially oscillating field amplitude that directly translates into a modulation of the electron wave function that can be imaged in real space (see Fig. 1b).

Results

Conclusion