Computer simulation of models for orientational glasses

Abstract

Monte Carlo studies of two- and three-dimensional lattice models where quadrupoles interact with a nearest-neighbor Gaussian coupling are reviewed. None of these models has a thermodynamic glass phase transition at non-zero temperature like the Ising spin glass: rather, phase transitions at zero temperature occur that exhibit a dynamical freeze-in spread out over a wide temperature range and are characterized by a strongly non-exponential relaxation. The time-dependent glass order parameter, q(t), decays with time, t, compatible with a stretched exponential decay q( t) ∼ exp [− ( t/ τ) y ] with a strongly temperature-dependent exponent. While the static glass ‘susceptibility’ for isotropic orientational glasses diverges as x G ∼ T − γ 0 as T → 0, for the three-dimensional three-state Potts glass an exponential divergence is found, 1n x G ∼ T −2, implying that the system is at its lower critical dimension.