Noise correlations of two-dimensional Bose gases

Abstract

We analyze density-density correlations of expanding clouds of weakly interacting two-dimensional Bose gases below and above the Berezinskii-Kosterlitz-Thouless transition, with particular focus on short-time expansions. During time-of-flight expansion, phase fluctuations of the trapped system translate into density fluctuations, in addition to the density fluctuations that exist in in-situ. We calculate the correlations of these fluctuations both in real space and in momentum space, and derive analytic expressions in momentum space. Below the transition, the correlation functions show an oscillatory behavior, controlled by the scaling exponent of the quasi-condensed phase, due to constructive interference. We argue that this can be used to extract the scaling exponent of the quasi-condensate experimentally. Above the transition, the interference is rapidly suppressed when the atoms travel an average distance beyond the correlation length. This can be used to distinguish the two phases qualitatively.

10 pages, 11 figures

References in corpus (5)

• Spatial quantum noise interferometry in expanding ultracold atom clouds
• Camparison of the Hanbury Brown-Twiss effect for bosons and fermions
• Extension of Bogoliubov theory to quasi-condensates
• Critical Point of an Interacting Two-Dimensional Atomic Bose Gas
• Probing Phase Fluctuations in a 2D Degenerate Bose Gas by Free Expansion

Cited by in corpus (3)

• Observation of a Bilayer Superfluid with Interlayer Coherence
• Detecting Phase Coherence of 2D Bose Gases via Noise Correlations
• A phase microscope for quantum gases