Studying quantized vortices and their dynamics in exciton-polariton quantum fluid

Abstract

Recently, a new type of bosonic quasiparticle, the “exciton-polariton” has been studied, which has strong photon-exciton coupling in semiconductor microcavities. The system provides a great opportunity for quantum fluid dynamics research because it allows the control of quantized vortices in a driven-dissipative superfluid by direct optical manipulation and detection. In this study, we observed quantized vortices generated by the transfer of a non-resonant pump beam’s angular momentum onto the polariton. A large energy difference between the pumped electron-hole state and the polariton condensate requires a relaxation process of the hot carriers through phonon scattering. This has been widely believed to scatter the original quantum states of the incident light, such as momentum and angular momentum. Our result suggests that the orbital angular momentum is conserved within the polaritons through the relaxation process. We measured not only the creation but also the chirality and stability of these vortices, confirming that these are generated by orbital angular momentum transfer. Also, we present new possibilities for studying the interactions of vortices. This study will open further discussion on the relaxation mechanism using nonresonant pumps.