Nematic-liquid-crystal light scattering in a symmetry-breaking external field

Eidner, K.; Lewis, M.; Vithana, Hemasiri; Johnson, D.L.

doi:10.1103/physreva.40.6388

Cited by 25 publications

(5 citation statements)

References 7 publications

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“…Consequently, when this eigenmode is thermally excited, n and M do not relax back, but remain in a distorted state, which is now a new equilibrium state. A similar argument explains the critical eld of the usual Frederiks transition 13,16 and the experiments showing critical slowing down of uctuations in the usual NLCs at electric, 17 magnetic, 18 and optic 19 Frederiks transitions have been performed using different light scattering techniques.…”

Section: Response To the Magnetic Eldmentioning

confidence: 78%

Magneto-optic and converse magnetoelectric effects in a ferromagnetic liquid crystal

et al. 2014

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We have studied the response of ferromagnetic liquid crystals to external magnetic and electric fields, and compared it to the usual response of nematic liquid crystals (NLCs). We have observed effects, which are not present in a pure NLC and are a consequence of the coupling between the nematic director and the magnetization. The electro-optic effect, which is in the ferromagnetic phase the same as in the pure NLC, is accompanied by a converse magnetoelectric effect. The magneto-optic effect differs completely from the one observed in the pure NLC, where it is a quadratic effect and it only appears when a magnetic field larger than a critical field is applied perpendicular to the director. In the ferromagnetic NLC in addition to the response to the perpendicular field, there is also a qualitatively different response to the parallel field. Contrary to the pure NLC no critical field needs to be exceeded for the system to respond to a perpendicular field, but a critical field needs to be exceeded to observe a response to the field parallel to the director and antiparallel to the magnetization. The critical field is in this case two orders of magnitude smaller than the critical field of the magnetic Frederiks transition in the pure NLC. The experimental observations are well described by a simple macroscopic theory.

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Section: Response To the Magnetic Eldmentioning

confidence: 78%

Magneto-optic and converse magnetoelectric effects in a ferromagnetic liquid crystal

et al. 2014

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“…[223], Pieranski et al [224], Sefton et al [112], Eidner et al [225], Galatola (2261 and Galatola and Rajteri [227]. Because of micron wavelengths, the observed dynamics is extremely slow (1 Hz) and exhibits softening in the vicinity of a critical field.…”

Section: Other Observationsmentioning

confidence: 99%

Nematic Liquid Crystals: Physical Properties, Section 2.6

Blinc¹,

Muševič²,

Demus³

et al. 1998

Handbook of Liquid Crystals

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The nematic liquid crystalline state is characterized by long-range orientational order of the average direction of the long molecular axis. Similar to the case of a Heisenberg ferromagnet it is a state of a spontaneously broken continuous orientational symmetry of the high temperature phase, that is, of the isotropic liquid phase. As a consequence, the spectrum of collective excitations of the nematic director field is expected to be gapless in the long-wavelength limit and the so-called Goldstone mode should exist [ 1-31.For finite wavelengths, the collective dynamics of bulk nematics can be described within the hydrodynamic equations of motion introduced by Ericksen [4-81 and Leslie [9-111. A number of alternate formulations of hydrodynamics [12-181 leads essentially to the equivalent results [19]. The spectrum of the eigenmodes is composed of one branch of propagating acoustic waves and of two pairs of overdamped, nonpropagating modes. These can be further separated into a low-and high-frequency branches. The branch of slow modes corresponds to slow collective orientational relaxations of elastically deformed nematic structure, whereas the fast modes correspond to overdamped shear waves, which are similar to the shear wave modes in ordinary liquids.In the long-wavelength limit, the relaxation rates for both modes are proportional to q2 which is characteristic of hydrodynamic modes. Here q is the wave-vector of the overdamped mode.

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“…²ÂÊÎÑÉÇÐËâ ÍÑÓÓÇÎâÙËÑÐÐÑÌ ×ÖÐÍÙËË Ä ÓâAEÞ ÒÑ ÔÑÃÔÕÄÇÐÐÞÏ ÏÑAEÂÏ ×ÎÖÍÕÖÂÙËÌ ËÊ ÓÂÃÑÕ [90,92,93] ÒÑÎÖÚÂÇÕÔâ, ÇÔÎË ÄÞÓÂÉÇÐËÇ (2.50) ÓÂÊÎÑÉËÕß ÍÂÍ ÏÇÓÑ-ÏÑÓ×ÐÖá ×ÖÐÍÙËá q c ÐÂ ÒÓÑÔÕÞÇ AEÓÑÃË.…”

Section: ¶îöíõöâùëë ä Aeäöøñôðþø¯¨¬unclassified