CRITICAL AMPLITUDE RATIOS FOR CRITICAL WETTING IN 3 DIMENSIONS - OBSERVATION OF NONCLASSICAL BEHAVIOR IN THE ISING-MODEL

The surface-layer susceptibility chi-1 is investigated for critical wetting transitions in three dimensions. Whereas mean-field treatments predict that chi-1 diverges symmetrically at the transition, a renormalization-group (RG) analysis predicts that the critical amplitude ratio R should be a rapidly increasing function of the parameter-omega that determines the strength of interfacial fluctuations. Existing Monte Carlo data for the simple-cubic Ising model show pronounced asymmetry in chi-1 and yield a value for the ratio R that is significantly greater than the mean-field result (unity). The data are consistent with RG predictions, provided omega approximately 0.3 for the Ising model at the temperature of the simulation.