ε-Expansion for the interfacial profile in an external field

The interfacial profile for the order parameter is calculated for a system with a LGW-Hamiltonian extended with an external field coupling to the order parameter. The calculation is restricted to the vicinity of the critical point and is carried out to first order in the ε-expansion. The profile is found to be a universal function of a scaled distance and temperature, such that the potential parameter is absorbed in the scaling. The field localizes and distorts the profile and both effects are incorporated correctly to order ε.