Superfluid behaviour of a two-dimensional Bose gas

By R. Desbuquois, L. Chomaz, T. Yefsah, J. L'eonard, J. Beugnon, C. Weitenberg, J. Dalibard. Nature Physics, 2012

167 citations recorded by the source corpus.

Two-dimensional Bose fluids—such as liquid-helium films, or confined ultracold atoms—cannot form a condensate, but become superfluid instead. Frictionless flow, proving superfluid behaviour, has now been observed in an ultracold two-dimensional Bose gas that is stirred with a laser beam. Owing to thermal fluctuations, two-dimensional (2D) systems cannot undergo a conventional phase transition associated with the breaking of a continuous symmetry1. Nevertheless they may exhibit a phase transition to a state with quasi-long-range order via the Berezinskii–Kosterlitz–Thouless (BKT) mechanism2. A paradigm example is the 2D Bose fluid, such as a liquid helium film3, which cannot condense at non-zero temperature although it becomes superfluid above a critical phase space density. The quasi-long-range coherence and the microscopic nature of the BKT transition were recently explored with ultracold atomic gases4,5,6. However, a direct observation of superfluidity in terms of frictionless flow is still missing for these systems. Here we probe the superfluidity of a 2D trapped Bose gas using a moving obstacle formed by a micrometre-sized laser beam. We find a dramatic variation of the response of the fluid, depending on its degree of degeneracy at the obstacle location.

Subfields: Atomic and Molecular Physics, and Optics

View Paper: https://www.semanticscholar.org/paper/4d11a8a615af4a894708e43a1ef8161756c81b13

Citations in the corpus

• Quantum simulation of the Hubbard model with ultracold fermions in optical lattices (2018, unknown): “In principle, this may be realized via the observation of vortices in rotating gases or by studying the response of the gas to a moving obstacle, as done for homogeneous Bose and Fermi gases [105,106,107,108].”