Visualising Berry phase and diabolical points in a quantum exciton-polariton billiard

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 Berr...

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Bibliographic Details
Published in:	Scientific reports 2016-11, Vol.6 (1), p.37653-37653, Article 37653
Main Authors:	Estrecho, E, Gao, T, Brodbeck, S, Kamp, M, Schneider, C, Höfling, S, Truscott, A G, Ostrovskaya, E A
Format:	Article
Language:	eng
Subjects:	Billiards Eigen values Energy Geometry Physics Symmetry
Online Access:	Get full text
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Summary:	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.
ISSN:	2045-2322 2045-2322