  With the intent of exploring how the interplay between boundary effects and
chiral symmetry breaking may alter the thermodynamical behavior of a system of
strongly interacting fermions, we study the Casimir effect for the setup of two
parallel layers using a four-fermion effective field theory at zero density.
This system reveals a number of interesting features. While for infinitely
large separation (no boundaries), chiral symmetry is broken or restored via a
second order phase transition, in the opposite case of small (and, in general,
finite) separation the transition becomes first order, rendering effects of
finite size, for the present setup, similar to those of a chemical potential.
Appropriately moving on the separation-temperature plane, it is possible to
generate a peculiar behavior in the temperature dependence of the thermodynamic
potential and of the condensate, compensating thermal with geometrical
variations. A behavior similar to what we find here has been predicted to occur
in bilayer graphene. Chiral symmetry breaking induces different phases
(massless and massive) in the Casimir force separated by critical lines.
