Pattern formation at the traveling liquid-crystal twist-grain-boundary–smectic-Ainterface

The different patterns observed at a twist-grain-boundary– (${\mathrm{TGB}}_{\mathit{A}}$–) smectic-A (A) interface moving in a temperature gradient are quantified by measuring interface arclength scaling between two lengths characterizing these patterns. The ragged melting ${\mathrm{TGB}}_{\mathit{A}\mathrm{-}}$A interface results from the growth of ${\mathrm{TGB}}_{\mathit{A}}$ filaments into oriented A. We attribute the destruction of ${\mathrm{TGB}}_{\mathit{A}}$ when A grows into ${\mathrm{TGB}}_{\mathit{A}}$ to the second-order nature of the ${\mathrm{TGB}}_{\mathit{A}}$-cholesteric transition. These results are interpreted within a defect lattice model.