Phase transitions in driven lattice gases

We have studied nonequilibrium lattice gases whose particles are driven by a field. The lattice is either a half-occupied square lattice or else the union of two energetically uncoupled ones. Monte Carlo simulations of the latter, which is always crossed by a dissipative particle current, show a tricritical point and a continuum of Ising-like critical points as the field is decreased, in addition to non-Ising, anisotropic critical behavior at higher temperatures for saturating fields. A comparison of the various phase transitions involved, and a detailed study of scaling of correlations with system size, indicate the relevance of the anisotropic liquid-vapor interface (rather than the driving field) for inducing non-Ising behavior in a class of systems. It is likely that some of the properties reported here are experimentally observable. {} 1996 The American Physical Society.