Hydrodynamic magneto-transport in holographic charge density wave states

We employ hydrodynamics and gauge/gravity to study magneto-transport in phases of matter where translations are broken (pseudo-)spontaneously. First we provide a hydrodynamic description of systems where translations are broken homogeneously at nonzero lattice pressure and magnetic field. This allows us to determine analytic expressions for all the relevant transport coefficients. Next we construct holographic models of those phases and determine all the DC conductivities in terms of the dual black hole geometry. Combining the hydrodynamic and holographic descriptions we obtain analytic expression for the AC thermo-electric correlators. These are fixed in terms of the black hole geometry and a pinning frequency we determine numerically. We find an excellent agreement between our hydrodynamic and holographic descriptions and show that the holographic models are good avatars for the study of magneto-phonons.

DIELECTRIC MEASUREMENTS ON PURE AND KDP ADDED DISODIUM HYDROGEN PHOSPHATE (DSHP) SINGLE CRYSTALS

Electrical conductivity is an elegant experimental tool to probe the structural defects and internal purity of crystalline solids. In the present study we have grown pure and KDP added DSHP single crystals by the slow evaporation method from aqueous solutions at room temperature. Good quality transparent crystals have been obtained. Melting point and density measurements were done. Electrical conductivity measurements were carried out with two frequencies, 100 Hz and 1 kHz at various temperatures ranging from 2 to 30oC by using the parallel plate capacitor method. The present study indicate that the dielectric constant and AC and DC conductivities increase with increase of temperature.

Influence of LiCl and AgNO3 Doping on the Electrical Conductivity of PVA Flexible Electrolyte Polymer Film

Recently, the electrical conductive electrolyte based on flexible polymeric films have been attracted much attentions, due to their applications in batteries, thermoelectrics, temperature sensors and others. In this regard, two polymeric electrolytes (PVA/LiCl) and (PVA/AgNO3) films have been engineered and the influence of the dopants and the annealing temperature on the structural, morphology and ac and dc conductivities is extensively studied. It was found that the films crystallinity has the order PVA/AgNO3 (49.44%) > PVA (38.64%) > PVA/LiCl (26.82%). Additionally, the dc conductivity of the films is increased with embedding the dopants into the PVA as the order PVA/AgNO3 (13.7 × 10−4 S/cm) > PVA/LiCl (1.63 × 10−5 S/cm) > PVA (1.71 × 10−6 S/cm) at 110 °C. It is also found that there is a sharp increase for σac as the frequency increases up to 107 Hz and also as the temperature increases to 110 °C. However, the order of increasing the σac is PVA/LiCl (155 × 10−3 S/cm) > PVA/AgNO3 (2.5 × 10−5 S/cm) > PVA (2 × 10−6 S/cm) at f = 107 Hz and 110 °C. The values of exponent are 0.870, 0.405 and 0.750 for PVA, PVA/AgNO3 and PVA/LiCl, respectively, and it is increased as the temperature increases for PVA and PVA/LiCl, but it is decreased for PVA/AgNO3. The activation energies Ea are 0.84, 0.51 and 0.62 eV for PVA, PVA/AgNO3 and PVA/LiCl, respectively. Moreover, the values of activation energy for charge carrier migration Em are 0.60, 0.34 and 0.4 eV for PVA, PVA/AgNO3 and PVA/LiCl, respectively. By using a simple approximation, the carrier concentration, carrier mobility and carrier diffusivity are calculated, and their values are increased as the temperature increases for all samples, but they are higher for PVA/LiCl than that of PVA/AgNO3. These results are discussed in terms of some obtained parameters such as hopping frequency, free volume and chain mobility. Interestingly, the conduction mechanism was found to be the electronic charge hopping for PVA and PVA/LiCl films, however it was found to be the ionic charge diffusion (n < 0.5) for PVA/AgNO3 film. It has been predicted that these electrolytic films have a prospective applications in batteries design, temperature sensors, electronic and wearable apparatuses at an affordable cost.

Holographic DC conductivity for backreacted NLED in massive gravity

In this work a holographic model with the charge current dual to a general non-linear electrodynamics (NLED) is discussed in the framework of massive gravity. Massive graviton can break the diffeomorphism invariance in the bulk and generates momentum dissipation in the dual boundary theory. The expression of DC conductivities in a finite magnetic field are obtained, with the backreaction of NLED field on the background geometry. General transport properties in various limits are presented, and then we turn to the three of specific NLED models: the conventional Maxwell electrodynamics, the Maxwell-Chern-Simons electrodynamics, and the Born-Infeld electrodynamics, to study the parameter-dependence of in-plane resistivities. Two mechanisms leading to the Mott-insulating behaviors and negative magneto-resistivities are revealed at zero temperature, and the role played by the massive gravity coupling parameters are discussed.

DC conductivities and Stokes flows in Dirac semimetals influenced by hidden sector

In the holographic model of Dirac semimetals, the Einstein–Maxwell scalar gravity with the auxiliary U(1)-gauge field, coupled to the ordinary Maxwell one by a kinetic mixing term, the black brane response to the electric fields and temperature gradient has been elaborated. Using the foliation by hypersurfaces of constant radial coordinate we derive the exact form of the Hamiltonian and equations of motion in the phase space considered. Examination of the Hamiltonian constraints enables us, to the leading order expansion of the linearised perturbations at the black brane event horizon, to derive the Stokes equations for an incompressible doubly charged fluid. Solving the aforementioned equations, one arrives at the DC conductivities for the holographic Dirac semimetals.

Two new polymorphs of cis-perinone: crystal structures, physical and electric properties

The crystal structures of two polymorphs of cis-perinone (bisbenzimidazo[2,1-b:1′,2′-j]benzo[lmn][3,8]phenanthroline-6,9-dione, Pigment Red 194) were solved from single crystals obtained solvothermally from 1,2-dichlorobenzene or n-butanol at 220°C. Both crystal structures (space group P21/c) derive from stacking of flat molecules arranged due to π–π interaction. The melting points of these two polymorphs are 471°C and 468°C and their respective optical bandgaps are 1.94 eV and 1.71 eV. One of the polymorphs demonstrates drift and hopping mechanisms of electric conductivity, whereas the other one is dominated by the drift conductivity. The direct current (DC) electric conductivity of the samples are 4.77 × 10−13 S m−1 and 6.84 × 10−10 S m−1 at room temperature. The significant difference in DC conductivities can be explained by the dependence of the mobility and concentration of charge carriers on the structure of the samples.

Ion Transport in Glass-Forming Calcium Potassium Nitrate: From Complex Behaviours to Unexpected Simplicities

Re-examination of published conductivity spectra for 2Ca (NO3)2∙3KNO3 (CKN) in its molten and glassy states, in terms of the MIGRATION concept, has brought to light new links between elementary processes occurring within one picosecond and their successful outcomes, i.e. those which determine the DC conductivities. The starting point of this analysis is the transition at 378 K, which arises from a change from a decoupled to a coupled transport mechanism. Remarkably, while there is a change in the shape of the conductivity dispersion and a jump in its onset frequency, there is no change in the temperature dependence of DC conductivity. What emerges from the analysis is a surprising continuity in high-frequency behaviour, with the activation energy and volume for elementary displacements, Eed and Ved, remaining constant from 300 K in the glass up to 500 K in the melt. The ratio, Eed/Ved, turns out to be equal to our previously defined DC activation moduli for CKN, given by EDC(T)/VDC(T) and Tg/(dTg/dp) for charge transport in the melt and structural relaxation at Tg, respectively. It seems that, at very short times, molten CKN behaves just like an elastic solid. The importance of elastic forces for ionic transport in CKN is corroborated by the finding that the published value of the high-frequency shear modulus of glassy CKN, G¥, matches those of Eed/Ved and hence of both activation moduli. The detected continuity in the picosecond behaviour of CKN across the glass transition could provide a new link between fragile liquids and glassy materials in general.