Observation of grand-canonical number statistics in a photon Bose-Einstein condensate.
We report measurements of particle number correlations and fluctuations of a photon Bose-Einstein condensate in a dye microcavity using a Hanbury Brown-Twiss experiment. The photon gas is coupled to a reservoir of molecular excitations, which serve as both heat bath and particle reservoir to realize grand-canonical conditions. For large reservoirs, we observe strong number fluctuations of the order of the total particle number extending deep into the condensed phase. Our results demonstrate that Bose-Einstein condensation under grand-canonical ensemble conditions does not imply second-order coherence.
Institut für Angewandte Physik, Universität Bonn, Wegelerstraße 8, 53115 Bonn, Germany.
Julian
J
Schmitt
Institut für Angewandte Physik, Universität Bonn, Wegelerstraße 8, 53115 Bonn, Germany.
Tobias
T
Damm
Institut für Angewandte Physik, Universität Bonn, Wegelerstraße 8, 53115 Bonn, Germany.
David
D
Dung
Institut für Angewandte Physik, Universität Bonn, Wegelerstraße 8, 53115 Bonn, Germany.
Frank
F
Vewinger
Institut für Angewandte Physik, Universität Bonn, Wegelerstraße 8, 53115 Bonn, Germany.
Jan
J
Klaers
Institut für Angewandte Physik, Universität Bonn, Wegelerstraße 8, 53115 Bonn, Germany.
Martin
M
Weitz