Counter-flow instability of a quantum mixture of two superfluids

Year: 2015

Authors: Abad M., Recati A., Stringari S., Chevy F.

Autors Affiliation: INO-CNR BEC Center and Dipartimento di Fisica dell´Università di Trento, Povo, Italy; Technische Universität München, Garching, Germany Laboratoire Kastler-BrosselÉcole Normale Supérieure, CNRS, UPMC, Paris, France

Abstract: We study the instability of a mixture of two interacting counter-flowing superfluids. For a homogeneous system, we show that superfluid hydrodynamics leads to the existence of a dynamical instability at a critical value of the relative velocity v(cr). When the interspecies coupling is small the critical value approaches the value v(cr) = c(1) + c(2), given by the sum of the sound velocities of the two uncoupled superfluids, in agreement with the recent prediction of [Y. Castin, I. Ferrier-Barbut, C. Salomon, arXiv:1408.1326 (2014)] based on Landau´s argument. The crucial dependence of the critical velocity on the interspecies coupling is explicitly discussed. Our results agree with previous predictions for weakly interacting Bose-Bose mixtures and applies to Bose-Fermi superfluid mixtures as well. Results for the stability of transversally trapped mixtures are also presented.


Volume: 69 (5)      Pages from: 126  to: 131

More Information: This work has been supported by ERC through the QGBE and ThermoDynaMix grants, by Provincia Autonoma di Trento and by Region Ile de France (IFRAF). A.R. acknowledges support from the Alexander von Humboldt foundation and the hospitality of Prof. Wilhelm Zwerger at the TUM, where part of this work has been carried out.
KeyWords: Superfluid Mixture; Dynamical Instability; Bose; Gases
DOI: 10.1140/epjd/e2015-50851-y

Citations: 27
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