Proposal for detecting ring current via electron vortices.

In an intense circularly polarized laser field, the excitation of the atoms shows a strong dependence on the orbital helicity. The resonant excitation starting from the ground state with $ m = - 1 $m=-1 occurs much more easily in the left-handed circularly polarized (LCP with $ m = + 1 $m=+1) pulse than in the right-handed circularly polarized (RCP with $ m = - 1 $m=-1) pulse. In this Letter, we numerically demonstrate that the orbital-helicity-dependent two-photon-resonant excitation leads to the photoelectron vortex pattern in the polarization plane being sensitive to the sequence of the two counter-rotating circularly polarized pulses in xenon, which enables the detection of the ring currents associated with different quantum states. These results also provide an effective way for controlling the rotational symmetry of the electron vortex.