Twisting Relativistic Electrons Using Ultra-intense Circularly Polarized Lasers in the Radiation-dominated QED Regime

Relativistic vortex particles offer a promising avenue for investigating and manipulating processes in high-energy and nuclear physics, as they provide an additional degree of freedom in the form of orbital-angular-momentum (OAM). Despite the potential benefits, the generation and detection of these particles have proven to be a significant challenge. In this work, we present a new method for producing high-energy vortex electrons and $\gamma$-photons by colliding relativistic electrons with circularly polarized laser pulses in the radiation-dominated quantum electrodynamics (QED) regime. We use the laser-dressed vortex state to develop a nonlinear scattering theory, which allows us to understand the transfer of spin angular momenta (SAM) to intrinsic OAM in the highly nonlinear multi-photon process. The theory shows that electrons in the vortex state carry higher intrinsic OAM when radiation-reaction becomes significant, with the central OAM number proportional to the amount of energy taken by the $\gamma$-photon. This study provides an effective approach to generating high-energy vortex electron beams using laser intensities that are currently achievable. Additionally, the emission spectra of energetic electrons in vortex states are found to exhibit multi-peaks, which sets them apart from plane-wave electrons and makes them easier to distinguish.