Rotation of a liquid crystal by the Casimir torque

Rotation of a liquid crystal by the Casimir torque

Author(s):David A. T. Somers and Jeremy N. Munday
Citation(s):Phys. Rev. A 91, 032520 (2015)

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Abstract: We present a calculation of the Casimir torque acting on a liquid crystal near a birefringent crystal. In this system, a liquid crystal bulk is uniformly aligned at one surface and is twisted at the other surface by a birefringent crystal, e.g., barium titanate. The liquid crystal is separated from the solid crystal by an isotropic, transparent material such as SiO2. By varying the thickness of the deposited layer, we can observe the effect of retardation on the torque (which differentiates it from the close-range van der Waals torque). We find that a barium titanate slab would cause 5CB (4−cyano−4′−pentylbiphenyl) liquid crystal to rotate by 10 degrees∘ through its bulk when separated by 35 nm of SiO2. The optical technique for measuring this twist is also outlined.