Postquench entropy growth in a chiral clock model

Abstract

We numerically study quenches from a fully ordered state to the ferromagnetic regime of the chiral Z 3 clock model, where the physics can be understood in terms of sparse domain walls of six flavors. As in the previously studied models, the ballistic spread of entangled domain wall pairs generated by the quench leads to a linear growth of entropy with time, up to a time ℓ/2 v g in size - ℓ subsystems in the bulk, where v g is the maximal group velocity of domain walls. In small subsystems located in the bulk, the entropy continues to grow, approaching ln 3 , as domain walls traverse the subsystem and increment the population of the two oppositely ordered states, restoring the Z 3 symmetry. The latter growth in entropy is seen also in small subsystems near an open boundary in a nonchiral clock model. In contrast to this, in the case of the chiral model, the entropy of small subsystems near an open boundary saturates. We rationalize the difference in behavior in terms of qualitatively different scattering properties of domain walls at the open boundary in the chiral model. We also present empirical results for entropy growth, correlation spread, and energies of longitudinal-field-induced bound states of domain wall pairs in the chiral model.