Dynamical scaling and decay of correlations for spinodal decomposition at Tc

We have investigated the nonequilibrium critical dynamics of a two-dimensional, spin-exchange (i.e., conserved magnetization), kinetic Ising model following quenches to Tc from random initial states. As in the case of subcritical quenches, we observe dynamical scaling of the equal time order parameter correlation function G(r,t,t), but here the nonequilibrium correlation length grows as L(t)∼t1/z, where z=4/15 is the usual dynamic critical exponent for this system. Moreover, we find dynamical scaling for correlations with the initial condition G(r,0,t). The temporal decay of autocorrelations at Tc yields a critical exponent λc=1.96±0.05 for the nonequilibrium dynamics: G(r,0,t)Lc-λ(t)G(r/L(t)).