Twisted Electron Collisions for Circular Rydberg Excitation

Many quantum information and quantum simulation techniques make use of circular Rydberg states, taking advantage of their long lifetimes and strong dipole–dipole interactions.  Unfortunately, the production of these states remains technically challenging.  Here we investigate twisted electron collisions as an alternative technique for generating circular Rydberg states.  Twisted electrons carry quantized orbital angular momentum that can be transferred to the electronic state of the atom during excitation and offer a potentially efficient means of generating circular Rydberg states.  Using a fully quantum mechanical approach, we calculate total excitation cross sections for circular Rydberg states of hydrogen, rubidium, and cesium targets using Bessel electron beams, including the full beam structure and macroscopic target effects.  We find that twisted electrons with large opening angles and low energies significantly enhance excitation cross sections compared to plane-wave electrons. We trace this enhancement to large orbital angular momentum contributions from the projectile. Overall, our findings demonstrate that twisted-electron excitation may provide a feasible and potentially advantageous method for generating circular Rydberg states.