Orientational relaxation in Brownian rotors with frustrated interactions on a square lattice.

We present simulation results on the equilibrium relaxation of Brownian planar rotors based on a uniformly frustrated XY model on a square lattice. The rotational relaxation exhibits typical dynamic features of fragile supercooled liquids including the two-step relaxation. We observe a dynamic crossover from the high-temperature regime with Arrhenius behavior to the low-temperature regime with temperature-dependent activation energy. A consistent picture for the observed slow dynamics can be given in terms of the caging effect and thermal activation across potential barriers in the energy landscapes.