Macroscopic quantum self-trapping and Josephson oscillations of exciton polaritons

• Published in: Nature physics 2013-05, Vol.9 (5), p.275-279
• Main Authors: Abbarchi, M., Amo, A., Sala, V. G., Solnyshkov, D. D., Flayac, H., Ferrier, L., Sagnes, I., Galopin, E., Lemaître, A., Malpuech, G., Bloch, J.
• Format: Article
• Language: English
• Subjects: 639/766/119; 639/766/400/385; 639/766/483; Atomic; Classical and Continuum Physics; Complex Systems; Condensates; Condensed Matter Physics; Helium; letter; Mathematical and Computational Physics; Microcavities; Molecular; Nonlinearity; Optical and Plasma Physics; Oscillations; Oscillators; Photonics; Physics; Polaritons; Quantum theory; Semiconductors; Theoretical; Trapping; Tunnelling
• ISSN: 1745-2473; 1745-2481
• DOI: 10.1038/nphys2609

The Josephson effects that arise when two quantum states are coupled through a barrier are difficult to observe in optical systems because photon–photon interactions are so weak. Researchers have now demonstrated an optical realization of two such phenomena—macroscopic self-trapping and Josephson oscillations—using polariton condensates in overlapping microcavities. The coupling of two macroscopic quantum states through a tunnel barrier gives rise to Josephson phenomena 1 such as Rabi oscillations 2 , the a.c. and d.c. effects 3 , or macroscopic self-trapping, depending on whether tunnelling or interactions dominate 4 . Nonlinear Josephson physics was first observed in superfluid helium 5 and atomic condensates 6 , 7 , but it has remained inaccessible in photonic systems because it requires large photon–photon interactions. Here we report on the observation of nonlinear Josephson oscillations of two coupled polariton condensates confined in a photonic molecule formed by two overlapping micropillars etched in a semiconductor microcavity 8 . At low densities we observe coherent oscillations of particles tunnelling between the two sites. At high densities, interactions quench the transfer of particles, inducing the macroscopic self-trapping of polaritons in one of the micropillars 9 , 10 . The finite lifetime results in a dynamical transition from self-trapping to oscillations with π phase. Our results open the way to the experimental study of highly nonlinear regimes in photonic systems, such as chaos 11 , 12 , 13 or symmetry-breaking bifurcations 14 , 15 .