Efficient orbital angular momentum transfer between plasmons and free electrons

TL;DR

This paper demonstrates that large amounts of orbital angular momentum can be efficiently transferred from chiral plasmons in thin films to free electrons, enabling the generation of high-vorticity electrons with significant azimuthal energy.

Contribution

It introduces a method for efficient transfer of high orbital angular momentum from chiral plasmons to free electrons, supported by predictive simulations under realistic conditions.

Findings

Efficient absorption of high-vorticity chiral plasmons by electrons.

Generation of electrons with orbital angular momentum much greater than 6h.

Significant azimuthal kinetic energy in transferred electrons.

Abstract

Free electrons can efficiently absorb or emit plasmons excited in a thin conductor, giving rise to multiple energy peaks in the transmitted electron spectra separated by multiples of the plasmon energy. When the plasmons are chiral, this can also give rise to transfer of orbital angular momentum (OAM). Here, we show that large amounts of OAM can be efficiently transferred between chiral plasmons supported by a thin film and free electrons traversing it. Under realistic conditions, our predictive simulations reveal efficient absorption of $\ell\gg1$ chiral plasmons of vorticity $m\gg1$, resulting in an OAM transfer $\ell m\hbar\gg\hbar$. Our work supports the use of chiral plasmons sustained by externally illuminated thin films as a way of generating high-vorticity electrons, resulting in a remarkably large fraction of kinetic energy associated with motion along the azimuthal direction, perpendicular to the incident beam.