Séminaire du LPTMS: Simon Pigeon


11:00 - 12:00

LPTMS, salle 201, 2ème étage, Bât 100, Campus d'Orsay
15 Rue Georges Clemenceau, Orsay, 91405

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Controlling superfluid vortices in polariton fluids

Simon Pigeon (LKB, Université Pierre et Marie Curie, Paris)

Exciton-polaritons, microcavity half-matter half-light quasi-particles,  when resonantly driven exhibit a superfluid regime. Accordingly,  topological excitations similar to those predicted in equilibrium  superfluids may spontaneously appear. However, the non-equilibrium  nature of polaritons requires the system to be continuously pumped in  order to compensate for losses. This driving plays a key role in the  formation and dynamics of such topological excitations. Excited through  a resonant pumping, the coherent field driving the system imposes a  phase on the polariton fluid which inhibits the formation of vortices or  solitons. This unique feature of coherently driven polariton superfluids  has been used to trap vortices. To that purpose an engineered pumping  profile, alternating between spatial driven and non driven regions was  proposed and successfully implemented.

Based on this same idea of spatially engineered pumping profils, many  works done lately focused spontaneous formation of vortices in polariton  superfluids. For practical experimental reasons, such as high speeds,  small propagation length and a short lifetimes, the hydrodynamics of  these vortices propagating were largely ignored.

I will present a recent investigation of an optical method allowing us  to overcome these difficulties, together with giving the unique  opportunity to directly control and manipulate the properties of the  vortices. The general idea is to sustain the superfluid polariton flow,  something which generally does not last long outside the excitation  region, with a secondary supporting excitation of low intensity. This  way the flow may propagate over a much longer distance. The vortices  formed in the superfluid are still permitted due to the weakness of the  support pump. This allows their propagation along large distances and  the observation of their hydrodynamic behaviour. However, the secondary  coherent driving acting as a support, allows for some other rich and  unique features. At the same time as increasing the propagation length,  the same support driving gives direct control over the vortex-antivortex  pair properties, offering a unique opportunity to manipulate vortex  locally and accurately.

The new approach proposed allows for the observation of hydrodynamic  behaviour of superfluid vortices, and initiates a new step regarding the  control of such fundamental entities, thus paving the way toward their  practical use.


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