SPONTANEOUS STRUCTURE FORMATION IN DRIVEN SYSTEMS WITH 2 SPECIES - EXACT-SOLUTIONS IN A MEAN-FIELD THEORY

A stochastic lattice gas of particles, subject to an excluded volume c onstraint and to a uniform external driving field, is investigated. Us ing a mean-field theory for a system with equal number of oppositely c harged particles, exact results are obtained. Focusing on the current- vs-density plot, we propose an explanation for the discontinuous trans ition found in earlier simulations. A critical value of the drive, bel ow which this transition becomes continuous, is found. These results a re supported by a bifurcation analysis, leading to an equation of moti on for the amplitude of the soft mode.