Spin-polarized electron vortices produced in single-photon ionization

We theoretically investigate a scheme to produce spin-polarized electrons based on the vortex interference of the photoelectrons in single-photon ionization. A pair of time-delayed counterrotating circularly polarized pulses are applied to ionize the rare-gas-atom krypton. The results show that the vortex-shaped photoelectron momentum distributions for the ionization channels of J = 1/2 and J = 3/2, as well as those associated with the initial p+ and p- orbitals, can be well dislocated in momentum space, leading to the spin polarization exceeding 50%. Furthermore, by modifying the time delay, the wavelength, and the relative phase of the pulse pair, we show that the kinetic energy as well as the ejection angle of the spin-polarized electrons can be flexibly controlled in the present scheme.