Fluctuation modes of a twist-bend nematic liquid crystal

Parsouzi, Z.; Shamid, S. M.; Borshch, V.; Challa, P. K.; Baldwin, A. R.; Tamba, M. G.; Welch, C.; Mehl, G. H.; Gleeson, J. T.; Jakli, A.; Lavrentovich, O. D.; Allender, D. W.; Selinger, J. V.; Sprunt, S.

Abstract

We report a dynamic light-scattering study of the fluctuation modes in a thermotropic liquid crystalline mixture of monomer and dimer compounds that exhibits the twist-bend nematic (NTB) phase. The results reveal a spectrum of overdamped fluctuations that includes two nonhydrodynamic modes and one hydrodynamic mode in the N TB phase, and a single nonhydrodynamic mode plus two hydrodynamic modes (the usual nematic optic axis or director fluctuations) in the higher temperature, uniaxial nematic phase. The properties of these fluctuations and the conditions for their observation are comprehensively explained by a Landau-de Gennes expansion of the free-energy density in terms of heliconical director and helical polarization fields that characterize the N TB structure, with the latter serving as the primary order parameter. A "coarse-graining" approximation simplifies the theoretical analysis and enables us to demonstrate quantitative agreement between the calculated and experimentally determined temperature dependence of the mode relaxation rates.

Citation

Parsouzi, Z., Shamid, S. M., Borshch, V., Challa, P. K., Baldwin, A. R., Tamba, M. G., Welch, C., Mehl, G. H., Gleeson, J. T., Jakli, A., Lavrentovich, O. D., Allender, D. W., Selinger, J. V., & Sprunt, S. (2016). Fluctuation modes of a twist-bend nematic liquid crystal. Physical Review X, 6(2), 021041-1-021041-16. https://doi.org/10.1103/PhysRevX.6.021041

• Journal Article Type: Article
• Acceptance Date: Feb 29, 2016
• Online Publication Date: Jun 22, 2016
• Publication Date: Jun 22, 2016
• Deposit Date: May 26, 2016
• Publicly Available Date: Jun 22, 2016
• Journal: Physical review x
• Electronic ISSN: 2160-3308
• Publisher: American Physical Society
• Peer Reviewed: Peer Reviewed
• Volume: 6
• Issue: 2
• Pages: 021041-1-021041-16
• DOI: https://doi.org/10.1103/PhysRevX.6.021041
• Keywords: Twist-bend nematic
• Public URL: https://hull-repository.worktribe.com/output/438775
• Publisher URL: https://journals.aps.org/prx/abstract/10.1103/PhysRevX.6.021041
• Additional Information: This is a copy of an open access article published in Physical review x, 2016, v.6.
• Contract Date: May 26, 2016