Phase stripe formation

Raman scattering as a function of 7.4. Phase separation due to stripe formation ... 

Shanna et al. (2000) discuss their results in conjunction with the stripe-phase scenario (Emery et al. 1997). The assignment of Ti to the stripe formation temperature where... 

Figure 10 Dissipative structures fonned in casting polymer solution (a) Benard cells and lingering instability fonned in chloroform solution of polyion complex of 1 and 11 (b) snapshots of stripe formation from the fingering instability at the three-phase line synchronized with receding front (c) regularly arrayed polymer dots formed by dewetting in the stripes.

Neutron scattering experiments also detected static charge stripes in the low-temperature tetragonal (LTT) phase of lanthanum cuprates Lai 6-. rNdo 4Ba tCu04 and La2- BajrCu04 [16-19]. One of the manifestations of the stripe formation is the anomalous suppression of superconductivity near the hole concentration x = in the latter crystal. A weaker... 

A variety of munerical methods have been used to elucidate the existence of phase separation in the groimd states of the Hubbard and models of the Cu-0 planes of cuprate perovskites. States with charge density waves (CDW), which can be interpreted as stripes, were obtained in Refs. [24-26,29-32] by using the mean-field approximation, the variational principle with the Gutzwiller-type variational fimctions, and the density matrix renormalization group calculations. However, the results of the Monte Carlo simulations [33-35] and cluster calculations [36,37] cast doubt on this finding. Thus, the issue of whether a purely electronic mechanism can explain the stripe formation is still an open question. 

However, further analysis of the behavior of the system in LC cells cast doubt on this interpretation. First, while intuitively attractive, the idea that relaxation of the polarization by formation of a helielectric structure of the type shown in Figure 8.20 would lower the free energy of the system is not correct. Also, in a thermodynamic helical LC phase the pitch is extremely uniform. The stripes in a cholesteric fingerprint texture are, for example, uniform in spacing, while the stripes in the B2 texture seem quite nonuniform in comparison. Finally, the helical SmAPF hypothesis predicts that the helical stripe texture should have a smaller birefringence than the uniform texture. Examination of the optics of the system show that in fact the stripe texture has the higher birefringence. 

A conglomerate in real liquid crystalline phases was first observed in the smectic phase of a rod-shaped mesogen with two stereogenic centers in its tail [42], We used a racemic mixture which was supposed not to electrically switch. Evidence for conglomerate formation was provided by clear electro-optic switching and texture observation under a polarizing microscope domains with stripes, which themselves display fine stripes. These stripes are tilted in two different directions with respect to the primary stripes. This is a still very rare example now that fluid soft matter is known to resolve spontaneously into a three-dimensional conglomerate. 

The critical densities for the formation of the electronic polaronic crystals depend on the effective volume occupied by the doped charge carriers. The anisotropic interactions between the doped charge carriers produce the stripe or checkboard phases [15-16],... 

Now possibilities of the MC simulation allow to consider complex surface processes that include various stages with adsorption and desorption, surface reaction and diffusion, surface reconstruction, and new phase formation, etc. Such investigations become today as natural analysis of the experimental studying. The following papers [282-285] can be referred to as corresponding examples. Authors consider the application of the lattice models to the analysis of oscillatory and autowave processes in the reaction of carbon monoxide oxidation over platinum and palladium surfaces, the turbulent and stripes wave patterns caused by limited COads diffusion during CO oxidation over Pd(110) surface, catalytic processes over supported nanoparticles as well as crystallization during catalytic processes. 

Coexistence of a SC and the IC AF phases at low temperatures was confirmed recently by the neutron diffraction experiments [31] for La2 xSrxCu04 (x = 0.10) in the vortex state. (The coexistence of SC and AF formations was found also from the //S11 spectra [32]). The way of the "coexistence of SC and the stripe order in the same sample remains unresolved one view treats the new stripe symmetry as a superstructure superimposed on the Fermi surface that changes the energy spectrum like any SDW/CDW can do it (e.g. [33]). Another plausible alternative would be a spatially inhomogeneous coexistence of the nonsuperconducting IC AF phase and a "metallic phase with strong fluctuations. 

Figure 8 Schematic illustration for the formation of SAMs of alkanethiolates on gold [73], (A) Alkanethiols adopt the highly mobile lattice-gas phase (B) above a critical value of coverage, striped-phase islands are formed (C) surface reaches saturation coverage of striped phase (D) surface undergoes lateral-pressure-induced solid phase transition high-density islands nucleate and grow at domain boundaries (E) high-density islands grow at the expense of the striped phase until the surface reaches saturation...

It is clear that surface reconstruction phenomena play an important role in electrochemical 2D and 3D phase formation processes. lindsay [2.11] has shown that in the underpotential range (cf. Chapter 3) 2D Pb monolayer domains are formed preferentially along the stripes of reconstructed Au(lll) surfaces. 

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