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arXiv · 2108.08840

Observation of the BKT Transition in a 2D Bose Gas via Matter-Wave Interferometry

Shinichi Sunami·Vijay P. Singh·David Garrick·Abel Beregi·Adam J. Barker·Kathrin Luksch·Elliot Bentine·Ludwig Mathey·Christopher J. Foot
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Abstract

We probe local phase fluctuations of trapped two-dimensional (2D) Bose gases using matter-wave interferometry. This enables us to measure the phase correlation function, which changes from an algebraic to an exponential decay when the system crosses the Berezinskii-Kosterlitz-Thouless (BKT) transition. We determine the temperature dependence of the BKT exponent $\eta$ and find the critical value $\eta_c = 0.17(3)$ for our trapped system. Furthermore, we measure the local vortex density as a function of the local phase-space density, which shows a scale-invariant behaviour across the transition. Our experimental investigation is supported by Monte Carlo simulations and provides a comprehensive understanding of the BKT transition in a trapped system.

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Shinichi Sunami, Vijay P. Singh, David Garrick, Abel Beregi, Adam J. Barker, Kathrin Luksch, Elliot Bentine, Ludwig Mathey, Christopher J. Foot. 2021-08-19. Observation of the BKT Transition in a 2D Bose Gas via Matter-Wave Interferometry. https://doi.org/10.1103/physrevlett.128.250402

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