A mixture of Bose and Fermi superfluids

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I. Ferrier-Barbut, M. Delehaye, S. Laurent, A. T. Grier, M. Pierce, B. S. Rem, F. Chevy, C. Salomon Science 345, 1035-1038 (2014)

Superfluidity and superconductivity, are striking signatures of quantum mechanics at the macroscopic level, resulting in extraordinary features like the absence of viscosity or resistance in superconducting metals. In liquid helium and dilute gases, Bose and Fermi superfluidity has been observed separately, but producing a mixture in which both the fermionic and the bosonic components are superfluid is challenging.

In their work, Ferrier-Barbut and co-workers report the observation of such a mixture with dilute gases of two lithium isotopes, lithium-6 and lithium-7. They probe the collective dynamics of this system by exciting center-of-mass oscillations that exhibit extremely low damping below a certain critical velocity. Using high- precision spectroscopy of these modes, they observe coherent energy exchange and measure the coupling between the two superfluids.