Probing superfluidity in a quasi two-dimensional Bose gas through its local dynamics

Camilla de Rossi (1, 2) , Romain Dubessy (2, 1) , Karina Merloti (2, 1) , Mathieu de Goër de Herve (1, 2) , Thomas Badr (1, 2) , Aurélien Perrin (1, 2) , Laurent Longchambon (1, 2) , Hélène Perrin (1, 2)

1 Condensat de Bose-Einstein
2 LPL - Laboratoire de Physique des Lasers

We report direct evidence of superfluidity in a quasi two-dimensional Bose gas by observing its dynamical response to a collective excitation. Relying on a novel local correlation analysis, we are able to probe inhomogeneous clouds and reveal their local dynamics. We identify in this way the superfluid and thermal phases inside the gas and locate the boundary at which the Berezinskii--Kosterlitz--Thouless crossover occurs. This new analysis also allows to evidence the coupling of the two fluids which induces at finite temperatures damping rates larger than the usual Landau damping.

Domaines: Gaz Quantiques [cond-mat.quant-gas]

Camilla de Rossi, Romain Dubessy, Karina Merloti, Mathieu de Goër de Herve, Thomas Badr, et al.. Probing superfluidity in a quasi two-dimensional Bose gas through its local dynamics. New Journal of Physics, 2016, 18, pp.062001. ⟨hal-01280816v2⟩