Exclusion processes with internal states

We introduce driven exclusion processes with internal states that
serve as generic transport models in various contexts, ranging from
molecular or vehicular traffic on parallel lanes to spintronics.
The ensuing nonequilibrium steady states are controllable by
boundary as well as bulk rates. A striking polarization phenomenon
accompanied by domain wall motion and delocalization is discovered
within a mesoscopic scaling. We quantify this observation within an
analytic description providing exact phase diagrams. Our results
are confirmed by stochastic simulations.