Persistent, controllable circulation of a polariton ring condensate

Persistent circulation is a canonical effect of superfluidity. In previous experiments, quantized circulation has been observed in polariton condensates, usually far from equilibrium, but persistent current in the absence of any stirring has not been seen. We report here the direct observation of persistent circulation of a polariton condensate with no driving force and with no observable change in time. We can cause the condensate to circulate in either direction on demand using a short laser pulse, after which the condensate continues to circulate for dozens to hundreds of rotations around a ring trap without any further stimulation. Our theoretical model successfully shows how the pulse, despite not carrying any angular momentum, causes the circulation.