Interface potential and line tension for BoseEinstein condensate mixtures near a hard wall
Abstract
Within GrossPitaevskii (GP) theory we derive the interface potential V (ℓ ) which describes the interaction between the interface separating two demixed Bosecondensed gases and an optical hard wall at a distance ℓ . Previous work revealed that this interaction gives rise to extraordinary wetting and prewetting phenomena. Calculations that explore nonequilibrium properties by using ℓ as a constraint provide a thorough explanation for this behavior. We find that at bulk twophase coexistence, V (ℓ ) for both complete wetting and partial wetting is monotonic with exponential decay. Remarkably, at the firstorder wetting phase transition, V (ℓ ) is independent of ℓ . This anomaly explains the infinite continuous degeneracy of the grand potential reported earlier. As a physical application, using V (ℓ ) we study the threephase contact line where the interface meets the wall under a contact angle θ . Employing an interface displacement model we calculate the structure of this inhomogeneity and its line tension τ . Contrary to what happens at a usual firstorder wetting transition in systems with shortrange forces, τ does not approach a nonzero positive constant for θ →0 , but instead approaches zero (from below) in the manner τ ∝−θ as would be expected for a critical wetting transition. This hybrid character of τ is a consequence of the absence of a barrier in V (ℓ ) at wetting. For a typical V (ℓ )=S exp(−ℓ /ξ ) , with S the spreading coefficient and ξ a decay length, we conjecture that τ =−2 (1 −ln2 )γ ξ sinθ is exact within GP theory, with γ the interfacial tension and 0 ≤θ ≤π .
 Publication:

Physical Review A
 Pub Date:
 May 2022
 DOI:
 10.1103/PhysRevA.105.053309
 arXiv:
 arXiv:2201.04871
 Bibcode:
 2022PhRvA.105e3309V
 Keywords:

 Condensed Matter  Quantum Gases
 EPrint:
 18 pages, 15 figures