Off-critical Casimir effect in Ising slabs with antisymmetric boundary conditions in d=3

Abstract

The universal scaling function W+-(y) of the Casimir force (y is a temperature-dependent variable) away from the critical point for thermodynamic systems in the Ising universality class confined between two parallel plates with antisymmetric boundary conditions [denoted (ab)=(+-)] has been analyzed using the extended de Gennes-Fisher local-functional method. Results on the universal function W+-(y) are presented in spatial dimension d=3 applying the extended sine parametric model for temperatures T>TR, where TR is the critical temperature of the roughening transition. The asymptotic behavior of W+-(y) for large values of the scaling variable y, y→±∞, is analyzed in general dimension d for Tâ‰Tc, where Tc is the bulk critical temperature, and in d≥3 for Tâ‰TR. © 2013 American Physical Society.