Clock generator based on a vortex attractor in polariton superfluids

We reveal the topologically protected persistent oscillatory dynamics of a polariton superfluid which is driven nonresonantly by a super-Gaussian laser beam in a planar semiconductor microcavity subjected to an external C-shaped potential. We find persistent oscillations characterized by an attractor of vortices that are based on the dynamical behavior of small Josephson vortices rotating around the outer boundary of the ring-shaped dense region of the central vortex. The attractor is formed due to the inverse energy cascade accompanied by the growth of incompressible kinetic energy. The attractor displays a remarkable stability towards perturbations, and it may be tuned by the pump laser intensity to two distinct frequency ranges: 20.16±0.14 and 48.4±1.24pt0exGHz. This attractor is bistable with respect to the chirality of the vortex. The switching between two stable states is achieved by altering the pump power or by adding an extra incoherent Gaussian pump beam.