Rheology of twist-grain-boundary-A liquid crystals.

We report studies on the rheological properties of a liquid crystalline analog of Abrikosov phase in type-II superconductors known as twist-grain-boundary-A (TGB(A)) phase. The TGB(A) phase shows a large apparent yield stress compared to the cholesteric (N*) phase. The storage modulus (G') of the TGB(A) phase is significantly larger than the loss modulus (G''). The dynamic relaxation measurements indicate a solid-like behavior of N*, TGB(A), and smectic-C* phases. The complex shear modulus of the TGB(A) phase exhibits a power-law behavior G*(ω) ∼ ω(α) with α ≃ 0.5. The relative amplitude of G' and G'' at various temperatures indicate that the enhanced elasticity of TGB(A) phase is due to the structural defects.