Nematics with Quenched Disorder: Pinning out the Origin of Memory

Rotunno, Melissa; Buscaglia, Marco; Chiccoli, C.; Mantegazza, Francesco; Pasini, Paolo; Bellini, Tommaso; Zannoni, Claudio

doi:10.1103/physrevlett.94.097802

Cited by 38 publications

(37 citation statements)

References 17 publications

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“…In particular, we intend to study in detail external field loop hysteresis behavior in nonergodic regimes. We note that recent studies reveal that pinning of topological line defects in RF-type systems can play a significant role [63]. However, nematic and magnetic systems differ significantly with respect to line defect topology.…”

Section: Discussionmentioning

confidence: 66%

“…Extensive simulations [65,66] suggest that LRO is lost even at low D in the analogous magnetic models. The Larkin-Imry-Ma theory in the RAN case [49] suggests that the LRO should always be unstable at least with respect to the formation of domains, with short-range order, and this is in general what has been found in a number of studies on the SSS model [22,[61][62][63].…”

Section: Introductionmentioning

confidence: 76%

“…(1), the vector n i is a random vector at site i of the regular lattice, and all sites are subject to the random anisotropy term. The second lattice model is the SSS (sprinkled silica spin) model [22,[61][62][63], in which a proportion p of sites in a Lebwohl-Lasher lattice are frozen:…”

Section: Introductionmentioning

confidence: 99%

“…Zero-field cooled (ZFC) and field-cooled (FC) samples behave differently, and the history dependence is related to pinning of disclination lines [63]. Likewise in the simulated HPZ model, the magnetic analogue of the RAN model, quenched samples exhibit LIM domains [65].…”

Section: Introductionmentioning

confidence: 99%

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Computational studies of history dependence in nematic liquid crystals in random environments

et al. 2014

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Glassy liquid crystalline systems are expected to show significant history-dependent effects. Two model glassy systems are the RAN and SSS lattice models. The RAN model is a Lebwohl-Lasher lattice model with locally coupled nematic spins, together with uncorrelated random anisotropy fields at each site, while the SSS model has a finite concentration of impurity spins frozen in random directions. Here Brownian simulation is used to study the effect of different sample histories in the low temperature regime in a three dimensional (d = 3) model intermediate between SSS and RAN, in which a finite concentration p < pc (pc the percolation threshold) of frozen spins interacts with neighboring nematic spins with coupling W . Simulations were performed at temperature T ∼ TNI /2 (TNI the bulk nematic-isotropic transition temperature) for temperature-quenched and field-quenched histories (TQH and FQH respectively), as well as for temperature-annealed histories (AH). The first two of these limits represent extreme histories encountered in typical experimental studies. Using long-time averages for equilibrated systems, we calculate orientational order parameters and two-point correlation functions. Finite size-scaling was used to determine the range of the orientational ordering, as a function of coupling strength W, p and sample history. Sample history plays a significant role; for given concentration p, as disorder strength W is increased, TQH systems sustain quasi-long-range (QLRO) and short-range-order (SRO). The data are also consistent with a long-range order (LRO) phase at very low disorder strength. By contrast, for FQH, only LRO and QLRO occur within the range of parameters investigated. The crossover between regimes depends on history, but in general, the FQH phase is more ordered than than the AH phase, which is more ordered than the TQH phase. We detect also in the QLRO phase a domain-type structural pattern, consistent with ideas introduced by Giamarchi and Doussal [Phys. Rev. B 52, 1242Rev. B 52, (1995] on superconducting flux lattices. In phases in which short-range exponential order occurs, the orientational correlation length in the weak-disorder limit obeys Larkin-Imry-Ma scaling ξ ∼ D −2/(4−d) .

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Section: Discussionmentioning

confidence: 66%

Section: Introductionmentioning

confidence: 76%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Computational studies of history dependence in nematic liquid crystals in random environments

et al. 2014

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“…4 Although it seems a quite general behavior, the connection between the glass-like 4 dynamics of confined LC's and the nature of the porous topology, surface interactions and confinement-induced quenched disorder effects remains challenging. 21,22,23,24 The individual molecular dynamics of confined LC's is also strongly modified. Dielectric relaxation spectroscopy has been extensively used since it allows one to probe the rotationallibrational dynamics of the dipolar molecules around their short axis as well as tumbling relaxation modes around the local nematic director.…”

Section: Introductionmentioning

confidence: 99%