CUBIC SURFACE FIELDS AND THE FIELD-THEORY OF CRITICAL ADSORPTION

Starting from a semi-infinite lattice-gas model equivalent to a n.n. Ising model with a surface magnetic field H1(a field theory of critical adsorption is constructed. The resulting continuum Hamiltonian involves both a linear surface field h1 ̴ w and a (previously neglected) cubic surface field w̴H1. Since w has momentum dimension ε/2 in 4-s dimensions, it is potentially dangerous. A field-theoretical RG analysis of the model in 4 - e dimensions is presented. Our main findings are: I) a new fixed point with w* =O(e), ii) the w = 0 fixed point is infrared-stable at lowest nontrivial order, iii) w implies that the most relevant surface scaling field depends not only on hi but also on the surface enhancement c and iv) it gives rise to corrections to scaling. © 1990 IOP Publishing Ltd.