Static properties of Bose–Einstein condensate mixtures in semi-infinite space

•Double-parabola approximation applied to two-component Bose–Einstein condensates.•The interfacial tension.•Antonov transition and Antonov line.

Using double-parabola approximation (DPA) applied to Gross–Pitaevskii theory, the interfacial tension of Bose–Einstein condensate mixtures in semi-infinite system is obtained and shows that it is not vanishing at demix state K=1K=1, its value exactly coincides to wall tension of second component. A new kind of wetting phase transition (Antonov transition) is also considered within DPA and phase transition is first-order. Antonov line is thoroughly proved, too.