An acoustic black hole in a stationary hydrodynamic flow of microcavity   polaritons
  We report an experimental study of superfluid hydrodynamic effects in a one-dimensional polariton fluid flowing along a laterally patterned semiconductor microcavity and hitting a micron-sized engineered defect. At high excitation power, superfluid propagation effects are observed in the polariton dynamics, in particular, a sharp acoustic horizon is formed at the defect position, separating regions of sub- and super-sonic flow. Our experimental findings are quantitatively reproduced by theoretical calculations based on a generalized Gross-Pitaevskii equation. Promising perspectives to observe Hawking radiation via photon correlation measurements are illustrated. 
H. S. Nguyen, D. Gerace, I. Carusotto, D. Sanvitto, E. Galopin, A.   Lema\^itre, I. Sagnes, J. Bloch, and A. Amo
cond-mat.mes-hall cond-mat.quant-gas