Penrose processes in an analogue black hole formed in hybrid light-matter (polariton) superfluid

Nothing, not even light, can escape from a black hole due to extreme gravity. However, as was shown by Roger Penrose , massive particles entering the ergoregion just outside the event horizon can extract energy from a rotating black hole. We propose to explore this elusive, fascinating process in a table-top experimental quantum light-matter superfluid formed in a semiconductor microcavity polariton platform; this will emulate a rotating black hole in 2+1 dimensional analogue spacetime on a microscale. The research will capitalize on the highly favorable properties of the polariton system, such as the ability to undergo condensation and superfluidity due to the giant optical nonlinearity, as well as the ability to control, drive and measure the spatial density and phase of the 2D polaritons using external laser sources. These enable the "flow" of space-time in a black hole by a large draining vortex in a superfluid to be emulated, where the boundary of the transition from subsonic to supersonic flow recreates the event horizon. The particular focus of this proposal will be on the study of how the Penrose process is affected by the quantum behavior of the polariton fluid (described by macroscopic order) leading to quantization of orbital angular momentum of the analogue black hole. Overall our project addresses fundamental physics questions by exploiting state-of-the art semiconductor quantum technologies developed in the Physics Department and at the National Epitaxy Facility at the University of Sheffield: it relates general relativity to hydrodynamics and physics of macroscopically ordered light-matter states in solids and opens up new avenues in the study of quantum phenomena and gravity effects on the microscale.