Vortex beams of atoms and molecules

TL;DR

This paper demonstrates the first creation of vortex beams of atoms and molecules using diffraction off binary masks, opening new avenues for atomic physics research with orbital angular momentum.

Contribution

It is the first experimental realization of vortex beams for non-elementary particles like atoms and molecules, expanding the scope of vortex beam applications.

Findings

Observed vortex rings corresponding to different OAM states.

Achieved large coherence lengths and nanometric grating features.

Method applicable to most atomic and molecular gases.

Abstract

Angular momentum plays a central role in a multitude of phenomena in quantum mechanics, recurring in every length scale from the microscopic interactions of light and matter to the macroscopic behavior of superfluids. Vortex beams, carrying intrinsic orbital angular momentum (OAM), are now regularly generated with elementary particles such as photons and electrons, and harnessed for numerous applications including microscopy and communication. Untapped possibilities remain hidden in vortices of non-elementary particles, as their composite structure can lead to coupling of OAM with internal degrees of freedom. However, thus far, the creation of a vortex beam of a non-elementary particle has never been demonstrated experimentally. We present the first vortex beams of atoms and molecules, formed by diffracting supersonic beams of helium atoms and dimers, respectively, off binary masks made from transmission gratings. By achieving large particle coherence lengths and nanometric grating features, we observe a series of vortex rings corresponding to different OAM states in the accumulated images of particles impacting a detector. This method is general and can be applied to most atomic and molecular gases. Our results may open new frontiers in atomic physics, utilizing the additional degree of freedom of OAM to probe collisions and alter fundamental interactions.