Vertically Stacked Soliton‐Like Domain Walls in Nematic Liquid Crystals

Abstract

In the standard liquid crystal (LC) geometry, one generally finds a quasi‐parabolic director profile in the vertical direction, where the directors are aligned with an applied field in the center of the cell. In contrast, using a numerical energy minimization approach, we find that there are multiple metastable solutions where the director profile is oscillatory. At low voltages, we find small oscillations, which evolve into standard soliton‐like domain walls as the applied voltage is increased. We predict the thickness of the domain wall with a simple analytic model that gives a good comparison to our numerical calculations, in the standard domain wall regime. For dual‐frequency nematic LCs, the occurrence of this regime can be tuned by a change of the biasing frequency. Moreover, we investigate how domain walls can affect the optical properties of LC‐based devices. For instance, we find that the transmittance curve shifts to higher voltages as domain walls are introduced. This shift can be used to create an efficient tunable filter.

New quasiperiodic structures in nematic liquid crystals

“…The process of energy minimisation is well described in the literature for one dimension. 9 We briefly outline the additional considerations necessary to make it applicable to three dimensions. In the planar cell arrangement, the total free energy for a nematic LC is the sum of the bulk and surface energies,wherewhere the surface energies are of the Rapini Papoular form.…”

“…At the other surfaces we assume free end conditions where there is no change in the director profile as the surface is approached. In solving (9) and its analogous equation, it is easy to make a mistake due to the sheer number of terms present. The resulting y, f equations are used to check that the length of our LC director, found by taking the magnitude of -L, remains unity.…”

“…To understand our observations, we have extended recent theoretical work on one-dimensional horizontally oriented domain walls to develop a theory to explain the time-development of soliton-like domain walls in the presence of a spatially varying electric field. 9 The theory demonstrates that both oscillatory and straight domain walls are stable.…”

“…Recently, it was shown that domain walls could also be horizontally oriented, i.e., walls parallel to the surface of the LC cell. [5][6][7][8][9] Since the discovery of domain walls, topological defects have become a robust field of LC research, with extensive reviews, [10][11][12][13] in addition to the expansive field of LC display applications. [14][15][16][17][18][19][20][21][22][23] Domain walls have been shown to reduce into a pair of disclination lines at a critical field strength, in the pincement process.…”

Reconfigurable wearable antenna for 5G applications using nematic liquid crystals

“…[14] These anisotropic properties allow LCs to be manipulated through a balance of forces and torques due to an applied electric field and elastic effects, yielding a reconfigurable design where the bandwidth of the antenna can be easily and accurately tuned. [15,16] In the present work we will consider those LCs that exhibit orientational anisotropy but no positional anisotropiy, termed 'nematic' liquid crystals (NLCs).…”