Counter-flow instability of a quantum mixture of two superfluids

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 [1] 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.

5 pages, 2 figues

References in corpus (8)

• Many-Body Physics with Ultracold Gases
• Theory of ultracold Fermi gases
• Generation of dark-bright soliton trains in superfluid-superfluid counterflow
• Binary Quantum Turbulence Arising from Countersuperflow Instability in Two-Component Bose-Einstein Condensates
• Countersuperflow instability in miscible two-component Bose-Einstein condensates
• Sound propagation in elongated superfluid fermion clouds
• Stationary waves in a supersonic flow of a two-component Bose gas
• Critical velocities in two-component superfluid Bose gases

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