Abstract
Systems described by an symmetrical Hamiltonian are considered in a -dimensional film geometry at their bulk critical points. The critical Casimir forces between the film’s boundary planes , , are investigated as functions of film thickness for generic symmetry-preserving boundary conditions . The -dependent part of the reduced excess free energy per cross-sectional area takes the scaling form when , where are scaling fields associated with the variables and is a surface crossover exponent. Explicit two-loop renormalization group results for the function at dimensions are presented. These show that (i) the Casimir force can have either sign, depending on and , and (ii) for appropriate choices of the enhancements , crossovers from attraction to repulsion and vice versa occur as increases.
- Received 13 June 2008
DOI:https://doi.org/10.1103/PhysRevLett.101.100601
©2008 American Physical Society