Effective field approach to the Ising film in a transverse field

We study the phase transitions of the spin-1/2 Ising film in a transverse field within the framework of the effective field theory. We evaluate the critical 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=Js/J is smaller than a critical value Rc, the critical temperature Tc/J of the film is smaller than the bulk critical temperature Tc^B/J and approaches Tc^B/J as R increases further. On the other hand, if R>Rc, Tc/J is larger than both the bulk Tc^B/J and the surface Tc^S/J critical temperatures of the corresponding semi-infinite system, and approaches Tc^S as R increases further.Comment: 16 pages, 5 figures, elsart.cls (included