Dynamics of order reconstruction in nanoconfined twisted nematic cells with a topological defect

Abstract

Within the Landau-de Gennes theory, we have investigated the dynamics of s = ±1/2 twist disclinations in a twisted nematic cell, using the two-dimensional finite-difference iterative method. We explore the biaxial structure of the defect core and describe its dynamics as the cell gap decreases. At a critical value of d_c* ≈ 9ξ (here ξ is the characteristic length for order-parameter changes), the exchange solution is stable, while the defect core solution becomes metastable, where the system starts to stretch the defect structure and the biaxiality starts to propagate inside of the cell. Compared to the case with no initial disclination, the value at which the exchange solution becomes stable increases relatively. At a critical separation of d_c ≈ 7ξ, the system undergoes a biaxial transition, and the defect core merges into a biaxial wall with large biaxiality. This transition corresponds to the reconstruction of the nematic order already found in the bulk with no defect. The force reaches a maximum at d ≈ 9ξ and a local minimum at d ≈ 7ξ. The dynamic response shows the influence of surface viscosity.

Keywords:

• biaxial transition
• topological defect
• eigenvalue exchange
• Landau-de Gennes theory

Funding

This research was supported by the National Natural Science Foundation of China under [grant number 11374087] and the Key Subject Construction Project of Hebei Province University.