Coupled superfluidity of binary Bose mixtures in two dimensions

Abstract

We consider a two-component Bose gas in two dimensions at low temperature with short-range repulsive interaction. In the coexistence phase where both components are superfluid, inter-species interactions induce a nondissipative drag between the two superfluid flows (Andreev-Bashkin effect). We show that this behavior leads to a modification of the usual Berezinskii-Kosterlitz-Thouless (BKT) transition in two dimensions. We extend the renormalization of the superfluid densities at finite temperature using the renormalization group approach and find that the vortices of one component have a large influence on the superfluid properties of the other, mediated by the nondissipative drag. The extended BKT flow equations indicate that the occurrence of the vortex unbinding transition in one of the components can induce the breakdown of superfluidity also in the other, leading to a locking phenomenon for the critical temperatures of the two gases.

Berezinskii-Kosterlitz-Thouless Transition of Two-Component Bose Mixtures with Intercomponent Josephson Coupling

“…Our result suggests that properties of superfluidity for both component are independent of each other, and the non-dissipative drag between the two component known as Andreev-Bashkin effect [67,68] is negligible. The similar result has been reported by a work studying a twodimensional spin-1 spinor Bose system; the mass and spin superfluid densities take the same value for the antiferromagnetic ground state [69].…”

Weakly-Interacting Bose–Bose Mixtures from the Functional Renormalisation Group

“…This corresponds to the interaction between the phases of the two condensates. The effect of the superfluid drag increases as the temperature increases, having an important impact on the phase transition in two dimension [93]. Therefore, the current ansatz has a limited application for finite-temperature two-dimensional Bose-Bose gases.…”

Many-body and temperature effects in two-dimensional quantum droplets in Bose–Bose mixtures

“…The temperature is normalized to which is defined for a symmetric mixture according to 50 . It has been demonstrated that the interspecies interaction plays a minor role near the BKT critical temperature 51 , 52 . We see that the free energy F diverges like as the density goes to zero due to the presence of thermal fluctuations effects.…”