Wetting transitions and tricriticality in a three-component Bose-Einstein condensate

The interfacial phenomena in multicomponent Bose-Einstein condensates include a rich variety of wetting transitions. Previous studies of a wall-less, three-component system have primarily fo-cused on the continuous (critical) wetting transition, leaving the phase diagram incomplete. In this work, we present a complete theoretical description of this system at zero temperature based on the Gross-Pitaevskii theory and a semi-analytical double-parabola approximation. We derive the analytical conditions for both discontinuous (first-order) and continuous (critical) wetting transitions by calculating the grand potential and the associated interfacial tensions. Synthesizing these results, we construct the complete wetting phase diagram and, crucially, identify the tricritical point where the first-order and critical transition lines meet. This complete phase diagram provides a quantitative roadmap for future experiments exploring complex interfacial phenomena in quantum fluids.