Casimir Contribution to the Interfacial Hamiltonian for 3D Wetting

Area of Science:

• Physics
• Materials Science
• Surface Science

Background:

• Previous models of three-dimensional (3D) wetting transitions overlooked a crucial entropic or low-temperature Casimir contribution.
• This contribution is essential for accurately describing the binding potential between an unbinding interface and a wall.

Purpose of the Study:

• To derive the interfacial model for 3D wetting from a microscopic Landau-Ginzburg-Wilson Hamiltonian.
• To incorporate and analyze the effects of the Casimir term on wetting transitions and interfacial phenomena.

Main Methods:

• Exact derivation of the interfacial model from a Landau-Ginzburg-Wilson Hamiltonian.
• Analysis of fluctuation effects and their impact on wetting transition predictions.
• Numerical renormalization group (NRG) for studying critical wetting phenomena.

Main Results:

• The Casimir term modifies the interpretation of fluctuation effects, invalidating mean-field predictions when interfacial fluctuations are ignored.
• While the surface phase diagram remains unchanged, adsorption near first-order wetting transitions is significantly increased.
• Predicted critical singularities of tricritical wetting are altered, including 3D nonuniversality from interfacial fluctuations.

Conclusions:

• The study resolves a long-standing controversy regarding critical wetting by showing a narrow asymptotic regime.
• The growth of the parallel correlation length in critical wetting is characterized by an effective exponent, agreeing with Ising model simulations.
• The inclusion of the Casimir contribution provides a more complete understanding of wetting phenomena in three dimensions.