Cooperative Domain-Wall Dynamics in a Two-Dimensional Quasiclassical Holstein Model

We investigate charge-density-wave (CDW) coarsening in a two-dimensional quasiclassical Holstein model following thermal quenches into the ordered phase. Although the staggered CDW order parameter is nonconserved, domain-wall motion remains constrained by conservation of the microscopic electronic charge. The simulations exhibit apparent growth exponents between 1/4 and the Allen--Cahn value 1/2. These apparent exponents are primarily accounted for by the crossover kinetics =[D(T)/L][1+L times 2(T)/L 2], where L times(T) is a temperature-dependent crossover length. At low temperature, nearly binary occupations require compatible wall segments to rearrange cooperatively, producing the L(t) about t 1/4 limit. Thermal broadening creates partially occupied interfacial sites that permit local curvature-driven motion and restore L(t) about t 1/2 at late times. Fits to the measured growth rate, a dimensionless rate collapse, and a long-time large-system simulation consistently support this crossover picture. These results show that a microscopic conservation law can generate long-lived anomalous coarsening even when the emergent order parameter is nonconserved.