Observation of a single quantized vortex vanishment in exciton-polariton superfluids

We report the direct observation of a single quantized vortex vanishing from a microcavity exciton-polariton superfluid. Exciton-polariton vortices generated by a nonresonant Laguerre-Gaussian optical pumping beam reveal themselves in the energy-integrated emission image, representing a multimode entity consisting of the ground- and excited states. From the time-resolved spectroscopy measurements utilizing various LaguerreGaussian beam sizes, we find that the two lowest-energy states get populated and compete with each other, manifested by the change in their mutual population with the beam diameter. Furthermore, we study the transition from the excited state characterized by the finite orbital angular momentum (and a vortex in the direct space) to the ground state under pulsed excitation conditions. Our experimental findings are in excellent agreement with the numerical calculations employing the driven-dissipative Gross-Pitaevskii equation coupled with pumping reservoirs. Thus, our study provides an experimental and theoretical platform to investigate nonequilibrium vortex dynamics and manipulate multistate polariton condensates in semiconductor microcavities.