@article{EstrechoGaoBrodbecketal.2016,
  author    = {Estrecho, E. and Gao, T. and Brodbeck, S. and Kamp, M. and Schneider, C. and H{\"o}fling, S. and Truscott, A. G. and Ostrovskaya, E. A.},
  title     = {Visualising Berry phase and diabolical points in a quantum exciton-polariton billiard},
  series = {Scientific Reports},
  volume    = {6},
  journal   = {Scientific Reports},
  number    = {37653},
  doi       = {10.1038/srep37653},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-167496},
  year      = {2016},
  abstract  = {Diabolical points (spectral degeneracies) can naturally occur in spectra of two-dimensional quantum systems and classical wave resonators due to simple symmetries. Geometric Berry phase is associated with these spectral degeneracies. Here, we demonstrate a diabolical point and the corresponding Berry phase in the spectrum of hybrid light-matter quasiparticles—exciton-polaritons in semiconductor microcavities. It is well known that sufficiently strong optical pumping can drive exciton-polaritons to quantum degeneracy, whereby they form a macroscopically populated quantum coherent state similar to a Bose-Einstein condensate. By pumping a microcavity with a spatially structured light beam, we create a two-dimensional quantum billiard for the exciton-polariton condensate and demonstrate a diabolical point in the spectrum of the billiard eigenstates. The fully reconfigurable geometry of the potential walls controlled by the optical pump enables a striking experimental visualization of the Berry phase associated with the diabolical point. The Berry phase is observed and measured by direct imaging of the macroscopic exciton-polariton probability densities.},
  language  = {en}
}