The specific heat of thin films near the λ-transition: a Monte Carlo study of an improved three-dimensional lattice model

We study the finite size scaling behaviour of the specific heat of thin films in the neighbourhood of the lambda-transition. To this end we have simulated the improved two-component phi(4) model on the simple cubic lattice. We employ free boundary conditions in the short direction to mimic the vanishing order parameter at the boundaries of a He-4 film. Most of our simulations are performed for the thicknesses L-0 = 8, 16 and 32 of the film. It turns out that one has to take into account corrections alpha L-0(-1) 0 to obtain a good collapse of the finite size scaling functions obtained from different L-0. Our results are compared with those obtained from experiments on thin films of He-4 near the lambda-transition, from field theory and from previous Monte Carlo simulations.