  In the Widom-Rowlinson lattice gas, two particle species (A, B) diffuse
freely via particle-hole exchange, subject to both on-site exclusion and
prohibition of A-B nearest-neighbor pairs. As an athermal system, the overall
densities are the only control parameters. As the densities increase, an
entropically driven phase transition occurs, leading to ordered states with A-
and B-rich domains separated by hole-rich interfaces. Using Monte Carlo
simulations, we analyze the effect of imposing a drive on this system, biasing
particle moves along one direction. Our study parallels that for a driven Ising
lattice gas -- the Katz-Lebowitz-Spohn (KLS) model, which displays atypical
collective behavior, e.g., structure factors with discontinuity singularities
and ordered states with domains only parallel to the drive. Here, other novel
features emerge, including structure factors with kink singularities (best
fitted to |q|), maxima at non-vanishing wavevector values, oscillating
correlation functions, and ordering into multiple striped domains perpendicular
to the drive, with a preferred wavelength depending on density and drive
intensity. Moreover, the (hole-rich) interfaces between the domains are
statistically rough (whether driven or not), in sharp contrast with those in
the KLS model, in which the drive suppresses interfacial roughness. Defining a
novel order parameter (to account for the emergence of multistripe states), we
map out the phase diagram in the density-drive plane and present preliminary
evidence for a critical phase in this driven lattice gas.
