Kinetics of Dislocation Driven Coarsening at Large Quench Depth
University of California, Irvine
We report on the experimental measurements of the late time coarsening of a striped pattern in electroconvection. For electroconvection, a nematic liquid crystal is placed between two glass plates. An AC voltage is applied perpendicular to the plates. Above a critical value of the voltage, a pattern of stripes with two different wavevectors forms. We apply a sudden change in the ac voltage as a quench. This takes the system from below the critical voltage to above the critical voltage. The growth of the striped domains is monitored after the quench. Two types of boundaries are observed: a grain boundary of dislocations in one direction and a domain wall along the direction perpendicular to it. The growth of domains is driven by the annihilation of dislocations traveling parallel to the domain walls. Studies of the Swift-Hohenberg equation suggest that for large enough quenches, pinning forces oppose defect motion. This slows the coarsening dynamics. As the quench depth increases, the system eventually reaches a glassy state in which the dynamics are effectively frozen. We will discuss the possibility of defect pinning in our striped system.