First- and second-order phase transitions in a driven lattice gas with nearest-neighbor exclusion.
A lattice gas with infinite repulsion between particles separated by < or = 1 lattice spacing, and nearest-neighbor hopping dynamics, is subject to a drive favoring movement along one axis of the square lattice. The equilibrium (zero drive) transition to a phase with sublattice ordering, known to be continuous, shifts to lower density, and becomes discontinuous for large bias. In the ordered nonequilibrium steady state, both the particle and order-parameter densities are nonuniform, with a large fraction of the particles occupying a jammed strip oriented along the drive. The drive thus induces separation into high- and low-density regions in a system with purely repulsive interactions. Increasing the drive can provoke a transition to the ordered phase, and thereby, a sharp reduction in current.
Dickman
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Departamento de Física, ICEx, Universidade Federal de Minas Gerais, 30123-970 Belo Horizonte, MG, Brazil. dickman@fisica.ufmg.br