NOVEL PHASE-TRANSITIONS IN BIASED DIFFUSION OF 2 SPECIES

We investigate biased diffusion in a stochastic lattice gas with equal numbers of oppositely <<charged>> particles, interacting only through an excluded-volume constraint. Particle-particle exchanges are allowe d, but occur on a much slower time scale than the dominant particle-ho le exchanges. With increasing particle density, the system orders firs t into a charge-segregated state, and disorders again near complete fi lling, through first-order transitions which turn second order at high er densities. A set of mean-field equations reflects the variations of the density profiles in the different phases.