  We address the sliding thermodynamics of van der Waals-bonded bilayers by the
continuum elasticity theory. We attribute the robustness of the
ferroelectricity recently observed in h-BN and WTe2 bilayers to large monolayer
in-plane stiffness. We compute the electric susceptibility and specific heat in
the mean-field self-consistent phonon approximation. We compare critical
temperatures and electric switching fields with the observations.
