Effective field approach to the Ising film in a transverse field

Within the framework of the effective field theory, we examine the phase tr ansitions of the spin-1/2 Ising film in a transverse field. We study the cr itical temperature of the film as a function of the exchange interactions, the transverse field and the film thickness. We find that, if the ratio of the surface exchange interactions to the bulk ones R = J(s)/J is smaller th an a critical value R-c, the critical temperature T-c/J of the film is smal ler than the bulk critical temperature T-c(B)/J and as R is increased furth er, T-c/J approaches T-c(B)/J. On the other hand, if R > R-c, T-c/J is larg er than the bulk T-c(B)/J and the surface T-c(S)/J critical temperatures of the corresponding semi-infinite system and as R is increased further, T-c/ J approaches the surface critical temperature T-c(s)/J. (C) 1999 Published by Elsevier Science B.V. All rights reserved.