Vortices in Andreev–Bashkin Superfluids

William Frank Vinen

S. I. Shevchenko, D. V. Fil

A microscopic theory is developed for the Andreev-Bashkin effect in a superfluid two-component weakly nonideal Bose gas. An expression is obtained for the matrix of superfluid densities in the general case of two gases with different densities, particle masses, and scattering lengths. A method for the observation of a drag between superfluid components is proposed.

Jacopo Nespolo, G. E. Astrakharchik, Alessio Recati

We study a mixture of two superfluids with density–density and current–current (Andreev–Bashkin) interspecies interactions. The Andreev–Bashkin coupling gives rise to a dissipationless drag (or entrainment) between the two superfluids. Within the quantum hydrodynamics approximation, we study the relations between speeds of sound, susceptibilities and static structure factors, in a generic model in which the density and spin dynamics decouple. Due to translational invariance, the density channel does not feel the drag. The spin channel, instead, does not satisfy the usual Bijl–Feynman relation, since the f-sum rule is not exhausted by the spin phonons. The very same effect on one dimensional Bose mixtures and their Luttinger liquid description is analysed within perturbation theory. Using diffusion quantum Monte Carlo simulations of a system of dipolar gases in a double layer configuration, we confirm the general results. Given the recent advances in measuring the counterflow instability, we also study the effect of the entrainment on the dynamical stability of a superfluid mixture with non-zero relative velocity.

Lucy J. Campbell

Daniele Contessi, Donato Romito, Matteo Rizzi +1 more

The authors study a one-dimensional two-component Bose-Hubbard ring by means of tensor network methods and provide numerical evidence of the Andreev-Bashkin collisionless superfluid drag and its sensible increase close to the pair-superfluid onset.

Ertugrul Demircan