The BCS Pairing Instability in the Thermodynamic Limit

The superconducting pairing instability---as determined by a divergence of the two-particle susceptibility---is obtained in the mean field (BCS) approximation in the thermodynamic limit. The usual practice is to examine this property for a finite lattice. We illustrate that, while the conclusions remain unchanged, the technical features are very different in the thermodynamic limit and conform more closely with the usual treatment of phase transitions encountered in, for example, the mean-field paramagnetic-ferromagnetic transition. Furthermore, by going to the extreme dilute limit, one can distinguish three dimensions from one and two dimensions, in which a pairing instability occurs even for two particles.Comment: 4 pages + references, 4 figure

P-133: Variable Liquid Crystal Pretilt and Azimuth Angle using Stacked Alignment Layers

Abstrac

5.1: Optically Rewritable Liquid-Crystal Technology: A New Green E-Paper Approach

Abstract Optical rewritable E-paper is a valuable contribution to the green technology, as E-paper replaces usual paper with the same quality of image. The light printable rewritable paper is based on liquid crystal photoalignment and is suitable for labels and plastic card displays, price labels, E-albums, Eadvertisements. Introduction The idea of the electronic paper (E-paper) is to store and display information generated by computer on a light weight thin flexible and robust, yielded a writing time of 60 s). The alignment induced on a nematic LC by a photoaligned polymer film with azo-dye side groups was investigated [9]. The orientation of the LC molecules was be manipulated in a reversible manner by irradiating the film with a polarized light. The reversibility of the photo-induced alignment may allow recording and erasing of information in a LC display. The works mentioned above We will consider (i) development of new highly sensitive ORW photoaligning materials and layers; (ii) implementation of ORW liquid crystal structures, that are very durable, cheap and ready for the flexible challenge, contact printing of the polymer spacers and lamination; (iii) investigations of regimes of operation to allow to use cheap and low power consuming high efficient light sources such as blue LED as an alternative exposure light source instead of expensive and high power consuming mercury lamps or lasers. Results and Discussion Structure of ORW e-paper and them optical properties was investigated in our previous papers. In order to "print" some image on ORW e-paper, linear polarized light should be used [13] We investigate the influence of the optically addressing conditions on the stability and the speed for the reorientation process and describe optimal configuration of the STN cells for it. Best results are shown by thick TN LC cells with the thickness close to the third Mauguin minimum. Such TN cell rotates polarization plane on the angle equal to the twist angle of this cell for any wave length (wave guiding regime). Disadvantage this type display is small information capacity and very low resolution for graphic type display. STN LC display has larger information capacity and can be used for produce graphical information but such type cell requires a special optimization of its effective birefringence to obtain the optimal condition for operation in a blue region (440±10 nm), where the LED writing and erasing is the most efficien

Polarization-gratings approach to deformed-helix ferroelectric liquid crystals with subwavelength pitch

Electro-optical properties of deformed helix ferroelectric liquid crystal (DHFLC) cells are studied by using a general theoretical approach to polarization gratings in which the transmission and reflection matrices of diffraction orders are explicitly related to the evolution operator of equations for the Floquet harmonics. In the short-pitch approximation, a DHFLC cell is shown to be optically equivalent to a uniformly anisotropic biaxial layer where one of the optical axes is normal to the bounding surfaces. For in-plane anisotropy, orientation of the optical axes and birefringence are both determined by the voltage applied across the cell and represent the parameters that govern the transmittance of normally incident light passing through crossed polarizers. We calculate the transmittance as a function of the electric field and compare the computed curves with the experimental data. The theoretical and experimental results are found to be in good agreement

Construction of efficient blue AIE emitters with triphenylamine and TPE moieties for non-doped OLEDs

In this paper, by merging the hole-dominated triphenylamine (TPA) and tetraphenylethene (TPE) moieties together with different linkage positions, four derivatives of 1,2-bis[4'-(diphenylamino)biphenyl-4-yl]-1,2-diphenylethene (2TPATPE) were successfully synthesized with confirmed structures, and their thermal, optical and electronic properties were fully investigated. Thanks to the introduction of the meta-linkage mode on the TPE core, their p-conjugation length could be effectively restricted to ensure blue emission. The non-doped OLEDs based on these four emitters exhibit blue emissions from 443–466 nm, largely blue-shifted with respect to the green emission of 2TPATPE (514 nm). Meanwhile, good electroluminescence efficiencies with Lmax, C,max, and P,max of up to 8160 cd m-2 , 3.79 cd A-1, and 2.94 Im W-1 respectively, have also been obtained, further validating our rational design of blue AIE fluorophores