Manifestation of relative phase in dynamics of two interacting Bose-Bose droplets.

We study coherent dynamics of two interacting Bose-Bose droplets by means of the extended Gross-Pitaevskii equation. The relative motion of the droplets couples to the phases of their components. The dynamics can be understood in terms of the evolution of zero-energy modes recovering symmetries spontaneously broken by the mean field solution. A phase-dependent interaction potential and Josephson-junction-like equations are introduced to explain the observed behaviour. We show that the evolution of the droplets is a macroscopic manifestation of the hidden dynamics of their phases. The ocurrence of non-dissipative drag between the two supercurrents (Andreev-Bashkin effect) is discussed.