Non-equilibrium structures and slow dynamics in a two dimensional spin system with competitive long range and short range interactions

We introduce a lattice spin model that mimics a system of interacting particle through a short range repulsive potential and a long range attractive power law decaying potential. We performed a detailed analysis of the general equilibrium phase diagram of the model at finite temperature, showing that the only possible equilibrium pases are the ferromagnetic and the antiferromagnetic ones. We then studied the non equilibrium behavior of the model after a quench to subcritical temperatures, in the antiferromagnetic region of the phase diagram region, where the pair interaction potential behaves in the same qualitative way as in a Lennard-Jones gas. We found that, even in the absence of quenched disorder or geometric frustration, the competition between interactions gives rise to non--equilibrium disordered structures at low enough temperatures that strongly slow down the relaxation of the system.