Charles Rosenblatt

We study numerically the reconfiguration process of colliding m=1/2 strength disclinations in an achiral nematic liquid crystal (NLC). A Landau–de Gennes approach in terms of tensor nematic-order parameters is used. Initially, different pairs m1,m2 of parallel wedge disclination lines connecting opposite substrates confining the NLC in a plane-parallel cell of a thickness h are imposed: {1/2,1/2}, {−1/2,−1/2} and {−1/2,1/2}. The collisions are imposed by the relative rotation of the azimuthal angle θ of the substrates that strongly pin the defect end points. Pairs {1/2,1/2} and {−1/2,−1/2} “rewire” at the critical angle θc1=3π4 in all cases studied. On the other hand, two qualitatively different scenarios are observed for {−1/2,1/2}. In the thinner film regime h<hc, the disclinations rewire at θc2=5π4. The rewiring process is mediated by an additional chargeless loop nucleated in the middle of the cell. In the regime h>hc, the colliding disclinations at θc2 reconfigure into boojum-like twist disclinations.

(a) 3D visualization of a SmA divot measured by optical profilometry. (b) Polarized optical microscopy image showing the OS pattern between crossed polarizers, overlaid by the parameters used in our model. (c) Side view sketch showing the different parameters in our model.