Defect dynamics of colloidal antiferromagnetic tetratic phase confined quasi-2d

We experimentally realize an antiferromagnetic tetratic phase with short-range translation order and quasi-long-range four-fold bond orientational order. The experiments employed hard-sphere micron size colloidal particles confined between parallel plates. We verify theoretical predictions (PHYSICAL REVIEW LETTERS 128, 255501 (2022)) of topological order resulting in bound pairs of oppositely-oriented dislocations and free pairs of dislocations oriented at 90 degrees. We demonstrate movement of free defect pairs in the direction of their (total) Burgers vector, as well as spontaneous formation and annihilation of oppositely oriented sets of free defect pairs. Finally, we present a simple free-volume model explaining the spontaneous defect movement.