Phase Diagram of a Driven Lattice Gas of Two Species with Attractive Interactions
We study the phase diagram of an interacting lattice
gas of two species of particles and holes, driven out of equilibrium by a local hopping bias
(denoted by `E').
Particles interact by excluded volume and nearest-neighbor attractions. We present a detailed
Monte Carlo investigation of the phase diagram. Three phases are found, with a homogenous
phase at high temperatures and two distinct ordered phases at lower temperatures. Which ordered
phase is observed depends on the parameter f, which controls the ratio of the two types of
particles. At small f, there is nearly a single species, and a transition is observed into a
KLS-type ordered phase. At larger f, the minority species are sufficiently dense to form a
transverse blockage, and a sequence of two transitions are observed as the temperature is lowered.
First, a continuous boundary is crossed into an SHZ-type ordered phase,
then at a lower temperature
a first-order boundary is crossed into the KLS-type ordered phase. At some critical value of f
is a bicritical point, where the first-order line branches from the two continuous boundaries. We also
consider correlations in the homogenous phase, by constructing a continuum description and comparing
to the results of simulations. Long range correlations are present in both the theoretical results
and the simulations, though certain details of the theory do not fit the observations very well. Finally,
we examine the beahvior of three-point correlations in the single-species (KLS) limit. Nontrivial
three-point correlations are directly related to the nonzero bias E. We therefore consider the behavior
of the three-point correlations as a function of E. We find that the three-point signal
saturates very rapidly with E. There are some difficulties interpreting the data at small E.