Anisotropic renormalization of thermodynamic quantities above the nematic–smectic-<i>A</i>phase transition

Andereck, Barbara S.; Patton, Bruce R.

doi:10.1103/physreve.49.1393

Cited by 33 publications

(8 citation statements)

References 33 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, for pure 8CB the scalings are highly anisotropic (ν /ν ⊥ = 1.314), consistent with behavior seen in various other smectic liquid crystals [42]. Patton and Andereck have advanced a theory that this anisotropic scaling results from coupling between nematic director fluctuations and the smectic order parameter [43,44]. For 8CB confined to aligned aerosil gels, the ratio ν /ν ⊥ shows much weaker scaling anisotropy than in pure 8CB.…”

Section: High-temperature Correlationssupporting

confidence: 72%

Smectic liquid crystals in an anisotropic random environment

Liang

Leheny

2007

Phys. Rev. E

View full text Add to dashboard Cite

We report a high-resolution x-ray scattering study of the smectic liquid crystal octylcyanobiphenyl (8CB) confined to aligned colloidal aerosil gels. The aligned gels introduce orientational fields that promote long-range nematic order while imposing positional random fields that couple to the smectic density wave and disrupt the formation of an ordered smectic phase. At low densities of aerosil, the low-temperature scattering intensity is consistent with the presence of a topologically ordered XY Bragg glass phase that is predicted to form in response to such anisotropic quenched disorder. The observed features of the phase include an algebraic decay of the smectic correlations, which is truncated at large length scales due to the imperfect nematic order, and a power-law exponent that agrees closely with the universal value predicted for the XY Bragg glass. At higher aerosil densities, deviations from the XY Bragg glass form are apparent. At high temperature, the scattering intensity displays pre-transitional dynamic fluctuations associated with the destroyed nematic to smectic-A transition. The fluctuations obey quasi-critical behavior over an extended range of reduced temperature. The effective critical exponents for the correlation lengths and smectic susceptibility differ systematically from those of pure 8CB, indicating that coupling of the nematic order to the gel suppresses its role in the smectic critical behavior.

show abstract

Section: High-temperature Correlationssupporting

confidence: 72%

Smectic liquid crystals in an anisotropic random environment

Liang

Leheny

2007

Phys. Rev. E

View full text Add to dashboard Cite

show abstract

“…Thus, in addition to the "softness" of the nematic, fluctuations in the director orientation compete with the establishment of smectic order by exciting anisotropic elastic deformations in the smectic. The theory for such coupling is not yet complete nor are all the implications of this effect understood, but a selfconsistent one-loop model has been put forward [35]. This type of coupling leads to anisotropy in the correlation lengths parallel and perpendicular to the nematic director (a feature not present in a normal 3D-XY system) and a very gradual crossover from a broad weaklyanisotropic critical correlation regime ν || ≥ ν ⊥ (weak coupling limit) toward a strongly-anisotropic ν || = 2ν ⊥ regime (strong coupling limit).…”

Section: Smectic Coupling To Director Fluctuationsmentioning

confidence: 99%

Smectic ordering in liquid-crystal–aerosil dispersions. II. Scaling analysis

et al. 2003

View full text Add to dashboard Cite

Liquid crystals offer many unique opportunities to study various phase transitions with continuous symmetry in the presence of quenched random disorder (QRD). The QRD arises from the presence of porous solids in the form of a random gel network. Experimental and theoretical work support the view that for fixed (static) inclusions, quasi-long-range smectic order is destroyed for arbitrarily small volume fractions of the solid. However, the presence of porous solids indicates that finite-size effects could play some role in limiting long-range order. In an earlier work, the nematic -smectic-A transition region of octylcyanobiphenyl (8CB) and silica aerosils was investigated calorimetrically. A detailed x-ray study of this system is presented in the preceding Paper I, which indicates that pseudo-critical scaling behavior is observed. In the present paper, the role of finite-size scaling and two-scale universality aspects of the 8CB+aerosil system are presented and the dependence of the QRD strength on the aerosil density is discussed.

show abstract

“…Furthermore, these exponents have unequal values indicating an anisotropic divergence (n I /n \ y 1.1-1.4) of the correlation lengths. This should be contrasted with different theoretical approaches that predict either a) isotropic (n I~n\~nxy ) [10] or b) strongly anisotropic (n I~2 n \ ) [3,11] divergence or c) a crossover from isotropic to strongly anisotropic behaviour [3,7]. Although some aspects of the experimental results agree with predictions of one model or another, none of the existing theories can explain all features of the results obtained by X-ray diffraction, light scattering, and heat capacity measurements.…”

mentioning

confidence: 93%

“…This is called dn-Y coupling. This coupling could drive the transition weakly first order [6] and lead to anisotropic critical behaviour [7]. Significantly, the effects of dn-Y coupling cannot be avoided in experiments since a complete quenching of director fluctuations requires a magnetic field of hundreds of tesla [8].…”

mentioning

confidence: 99%

See 1 more Smart Citation

New insights into the nematic to smectic-A transition: X-ray measurements in a strong magnetic field

Primak¹,

Fisch

Kumar³

2003

Liquid Crystals Today

View full text Add to dashboard Cite

The nematic to smectic-A (NA) phase transition would appear to be the simplest example of a freezing transition in nature. However, it has proven to be one of the most challenging problems of liquid crystal science and equilibrium statistical mechanics. One quantitative method to study this transition, that yields high quality data of almost transparent interpretation, has been X-ray measurements of the divergence of smectic order correlations as the SmA phase is approached from the nematic side. However, even data from these experiments have proved difficult to interpret because of the imperfect magnetic alignment or ''mosaic spread'' of the nematic phase. This mosaic spread limits the experimental transverse resolution and hence affects the data very close to the transition. Previous studies employed magnetic fields of y0.1-0.8 T. The use of a high (5 T) field, in the work we recently completed, improved the effective transverse resolution by almost two orders of magnitude allowing us to obtain results essentially free of mosaic spread. The generally used technique for removing this effect has now been tested. The high field results shed new light on this transition and reveal a new and proper way to apply the mosaicity correction.

show abstract

Anisotropic renormalization of thermodynamic quantities above the nematic–smectic-Aphase transition

Cited by 33 publications

References 33 publications

Smectic liquid crystals in an anisotropic random environment

Smectic liquid crystals in an anisotropic random environment

Smectic ordering in liquid-crystal–aerosil dispersions. II. Scaling analysis

New insights into the nematic to smectic-A transition: X-ray measurements in a strong magnetic field

Contact Info

Product

Resources

About