Fluctuation Modes of a Twist-Bend Nematic Liquid Crystal

被引：40

作者：

Parsouzi, Z. ^{[1
]}

Shamid, S. M. ^{[1
]}

Borshch, V. ^{[2
,3
]}

Challa, P. K. ^{[1
]}

Baldwin, A. R. ^{[1
]}

Tamba, M. G. ^{[4
]}

Welch, C. ^{[4
]}

Mehl, G. H. ^{[4
]}

Gleeson, J. T. ^{[1
]}

Jakli, A. ^{[2
,3
]}

Lavrentovich, O. D. ^{[2
,3
]}

Allender, D. W. ^{[1
]}

Selinger, J. V. ^{[2
,3
]}

Sprunt, S. ^{[1
]}

机构：

[1] Kent State Univ, Dept Phys, Kent, OH 44242 USA

[2] Kent State Univ, Chem Phys Interdisciplinary Program, Kent, OH 44242 USA

[3] Kent State Univ, Inst Liquid Crystal, Kent, OH 44242 USA

[4] Univ Hull, Dept Chem, Kingston Upon Hull HU6 7RX, N Humberside, England

来源：

PHYSICAL REVIEW X | 2016年 / 6卷 / 02期

基金：

美国国家科学基金会; 英国工程与自然科学研究理事会;

关键词：

LIGHT-SCATTERING; PHASE; TRANSITION;

D O I：

10.1103/PhysRevX.6.021041

中图分类号：

O4 [物理学];

学科分类号：

0702 ;

摘要：

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 NTB 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 NTB 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.

引用

页数：16