Half-Integer Point Defects in the Q-Tensor Theory of Nematic Liquid Crystals

We investigate prototypical profiles of point defects in two-dimensional liquid crystals within the framework of Landau–de Gennes theory. Using boundary conditions characteristic of defects of index k/2, we find a critical point of the Landau–de Gennes energy that is characterised by a system of ordinary differential equations. In the deep nematic regime, $$b^2$$b2 small, we prove that this critical point is the unique global minimiser of the Landau–de Gennes energy. For the case $$b^2=0$$b2=0, we investigate in greater detail the regime of vanishing elastic constant $$L ightarrow 0$$L→0, where we obtain three explicit point defect profiles, including the global minimiser.