Chiral-specific electron-vortex-beam spectroscopy

Abstract

Chiral electron-vortex beams, carrying a well-defined orbital angular momentum (OAM) about the propagation axis, are potentially useful as probes of magnetic and other chiral materials. We present an effective operator, expressible in a multipolar form, describing the inelastic processes in which electron-vortex beams interact with atoms, including those present in Bose-Einstein condensates, involving exchange of OAM. We show clearly that the key properties of the processes are dependent on the dynamical state and location of the atoms involved as well as the vortex-beam characteristics. Our results can be used to identify scenarios in which chiral-specific electron-vortex spectroscopy can probe magnetic sublevel transitions normally studied using circularly polarized photon beams with the advantage of atomic-scale spatial resolution.