X-ray scattering study of smectic ordering in a silica aerogel

Clark, Noel A.; Bellini, Tommaso; Malzbender, Rainer M.; Thomas, Britt N.; Rappaport, Aaron G.; Muzny, Chris D.; Schaefer, Dale W.; Hrubesh, Lawrence W.

doi:10.1103/physrevlett.71.3505

Cited by 110 publications

(69 citation statements)

References 18 publications

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“…At this lengthscale, thermodynamic equilibrium states are strongly affected, and new rules appear to govern the nature and the temperature of phase transitions. 4,14,15,16,17 3…”

Section: Introductionmentioning

confidence: 99%

Molecular dynamics of a short-range ordered smectic phase nanoconfined in porous silicon

Guégan

Morineau

Lefort

et al. 2007

The Journal of Chemical Physics

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“…At this lengthscale, thermodynamic equilibrium states are strongly affected, and new rules appear to govern the nature and the temperature of phase transitions. 4,14,15,16,17 3…”

Section: Introductionmentioning

confidence: 99%

Molecular dynamics of a short-range ordered smectic phase nanoconfined in porous silicon

Guégan

Morineau

Lefort

et al. 2007

The Journal of Chemical Physics

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“…The use of short-ranged correlations, even though the density of the (fractal) aerogel has long-ranged correlations, is justified, since the orientations of its constituent silica strands, beyond their microscopic persistance length, are certainly short-range correlated [6,5]. We will focus here on the bahavior of the smectic in the (large) window of length scales between the intrinsic orientational correlation length of the aerogel and the distance between disorder-induced smectic dislocations.…”

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confidence: 99%

“…64.60Fr,05.40,82.65Dp The effects of quenched disorder on the properties of condensed matter systems continues to be a fascinating area of active research, which includes the study of disordered superconductors [1], charge density waves [2], Josephson junction arrays [3], and Helium in aerogel [4], to name a few. Some of this attention has focussed [5,6] on liquid crystals in the random environment of an aerogel. While a complete picture of aerogel-confined liquid crystals is still being developed [6], in this Letter we show that a smectic phase of these systems possesses strong anomalous elasticity, when subjected to an arbitrarily weak amount of quenched disorder.…”

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Dirt Softens Soap: Anomalous Elasticity of Disordered Smectics

Radzihovsky

Toner

1997

Phys. Rev. Lett.

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We show that a smectic in a disordered medium (e.g., aerogel) exhibits anomalous elasticity, with the compression modulus B(k) vanishing and the bend modulus K(k) diverging as k → 0. In addition, the effective disorder develops long ranged correlations. These divergences are much stronger than those driven by thermal fluctuations in pure smectics, and are controlled by a zero temperature glassy fixed point, which we study in an ǫ = 5 − d expansion. We discuss the experimental implications of these theoretical predictions. 64.60Fr,05.40,82.65Dp The effects of quenched disorder on the properties of condensed matter systems continues to be a fascinating area of active research, which includes the study of disordered superconductors [1], charge density waves [2], Josephson junction arrays [3], and Helium in aerogel [4], to name a few. Some of this attention has focussed [5,6] on liquid crystals in the random environment of an aerogel. While a complete picture of aerogel-confined liquid crystals is still being developed [6], in this Letter we show that a smectic phase of these systems possesses strong anomalous elasticity, when subjected to an arbitrarily weak amount of quenched disorder. This result has important experimental consequences.The anomalous elasticity of pure smectics was predicted sometime ago [7], and is characterized by bulk compressional and tilt moduli B(k) and K(k) which, respectively, vanish and diverge at long wavelengths (k → 0). This is a general property of all one-dimensional crystals in which the direction of the 1d ordering wavevector is chosen spontaneously. As a consequence of this spontaneous breaking of rotational symmetry, (a property of smectics but not of charge density waves) in such systems, compression can be relieved by smoothing out fluctuations (wrinkles in the smectic layers), so the effective layer compressional modulus B(k) vanishes at long wavelengths. Similarly, in the presence of fluctuations, a bending of smectic layers necessarily leads to a compression, which implies that the effective tilt modulus K(k) diverges at long wavelengths. Unfortunately, this thermally driven behavior in pure smectics is difficult to observe experimentally, because the effect is very weak (logarithmic) in 3d.The main ingredients necessary for anomalous elasticity, namely spontaneously broken rotational invariance, and fluctuations, both exist even at zero temperature in quenched disordered smectics. In this Letter we demonstrate the existence of anomalous elasticity in quencheddisordered smectics which is significantly stronger than the marginal anomalous elasticity of thermal smectics, and is described by a zero-temperature fixed point that is perturbatively accessible in d = 5 − ǫ dimensions. The elastic anomaly is much stronger in quenched disordered smectics because layer fluctuations are much larger, even at T = 0, than in a pure smectic at T > 0.One experimental signature of these divergences is in the smectic correlation length for smectics in aerogel, which has a different, univers...

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“…Number of experiments have been dedicated to study of new features of transitions in helium [1][2][3][4][5] or liquid crystals [6][7][8][9][10] when they are confined within the pores of an aerogel. Theoretical reconstruction of those phenomena has been attempted through various models [11][12][13][14][15][16].…”

Section: Introductionmentioning

confidence: 99%

Numerical study of phase transitions inside the pores of aerogels

Uzelac

Hasmy²,

Jullien³

1995

Journal of Non-Crystalline Solids

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Phase transitions inside the pores of an aerogel are investigated by modelizing the aerogel structure by diffusion-limited cluster-cluster aggregation on a cubic lattice in a finite box and considering q-states Potts variables on the empty sites interacting via nearest-neighbours. Using a finite size scaling analysing of Monte-Carlo numerical results, it is concluded that for q = 4 the transition changes from first order to second order as the aerogel concentration (density) increases. Comparison is made with the case q = 3 (where the first order transition is weaker in three dimensions) and with the case q = 4 but for randomly (non correlated) occupied sites. Possible applications to experiments are discussed.PACS numbers: 64.60-Ak, 05.50-Fh, 75.40-Mg Typeset using REVT E X * a short report of this work has been published in Phys. Rev. Lett. 74, 422 (1995).

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X-ray scattering study of smectic ordering in a silica aerogel

Cited by 110 publications

References 18 publications

Molecular dynamics of a short-range ordered smectic phase nanoconfined in porous silicon

Molecular dynamics of a short-range ordered smectic phase nanoconfined in porous silicon

Dirt Softens Soap: Anomalous Elasticity of Disordered Smectics

Numerical study of phase transitions inside the pores of aerogels

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