Ultrafast plasmonic rotors for electron beams.

The interaction between free electrons and laser-induced near-fields provides a platform to study ultrafast processes and quantum phenomena while enabling precise manipulation of electron wavefunctions through linear and orbital momentum transfer. Here, by introducing phase offset between two orthogonally polarized laser pulses exciting a gold nanorod, we generate a rotating plasmonic near-field dipole with clockwise and counterclockwise circulating orientations and investigate its interaction with a slow electron beam. Our findings reveal that the circulation direction of plasmonic fields plays a crucial role in modulating electron dynamics, enhancing coupling strength, and controlling recoil. Furthermore, synchronizing the interaction time of the electron beam with rotational dipolar plasmonic resonances results in significant transfer of angular momentum to the electron beams and deflects the electron wavepackets from their original trajectory. These findings highlight the potential of plasmon rotors for shaping electron wavepackets, offering promising applications in ultrafast microscopy, spectroscopy, and quantum information processing.