Table of contents

The minimum of 4-terminal conductance occurring as carrier density is tuned through its charge neutral point has proven to be a robust empirical feature of graphene, persisting with changes to temperature, applied magnetic field, substrate, and layer thickness, though the theoretical mechanisms involved in transport about this point—vanishing density of states, conventional band gap opening, and broken-symmetry quantum Hall mobility gaps—vary widely depending on the regime. In this paper, we report on observations of a regime where the 4-terminal conductance minimum ceases to exist: transport in monolayer graphene connected to bilayer graphene during the onset of the quantum Hall effect. This observed increase in conductance is accompanied by decreases in conductance at the half-filling of the Landau levels adjacent to the charge-symmetric, zero-energy level. As monolayer and bilayer graphene have distinct zero-energy levels that form about the charge neutral point, our observations suggest that competitions between the differing many-body orderings of these states as they emerge may underlie these anomalous conductances.

An experiment is proposed to distinguish between different laser-cluster atomistic models and their predictions. The induced transparency of rare-gas clusters, post-interaction with an extreme ultraviolet (XUV) pump-pulse, is predicted by using an atomistic hybrid quantum–classical molecular dynamics model. We find there is an intensity range for which an XUV probe-pulse has no lasting effect on the average charge state of a cluster after being saturated by an XUV pump-pulse: the cluster is transparent to the probe-pulse. Multiple complete experimental signals are calculated which include the effect of the pulse's spatial distribution as well as the cluster size distribution. The calculated experimental signals and trends are also accomplished with the addition of an ionization potential lowering model that results in effectively removing the induced transparency effect. Thus, the proposed experiment is expected to either find the new phenomenon of induced transparency in clusters or give strong evidence for the existence of the enhanced ionization phenomenon, ionization potential lowering, in nanoplasmas.

We study squeezing and entanglement in superposition of a class of nonlinear spin coherent states. We analyze these properties as a function of the coherence and superposition parameters, number of qubits and the Hamiltonians involved, by presenting analytical and numerical results. We specifically observe that a subclass of these states, the even non-linear cat states are maximally entangled and squeezed, while another related subclass, the odd non-linear cat states, are entangled but not squeezed at all.

We investigate photon transport in a waveguide coupled to two-level quantum emitters with long-range interactions. We derive an exact solution for transmission and reflection amplitudes in the framwork of real-space Hamiltonian. Our explicit formula allows for a complete description of photon transport in the presence of N quantum emitters with arbitrary non-local interactions. We apply this approach to single-photon transport in an one-dimensional waveguide coupled to two atoms with dipole-dipole interaction (DDI). Our numerical results confirm the Fano spectrum line shapes as a result of strong DDI, and demonstrate how the split of perfect reflection spectrum and the resonance transmission can be achieved by tuning the photon-atom and the atom-atom interactions.

The presence of the Brewster point in one-dimensional photonic crystals restricts the possibility of achieving full omni-directional reflection at large incident wave vectors. We show that it is possible to achieve omnidirectional reflection in both rarefied and refracting incident media utilising periodic structures consisting of three or more distinct layers with differing refractive indices. In these ternary periodic structures the Brewster condition is not satisfied simultaneously at all interface and so strong reflection bands are achievable at any angle of incidence and polarisation state. Combining the ternary structure with layer chirping is necessary to open the full omnidirectional band.

We consider two coupled quantum harmonic oscillators with different free frequencies. Here the interaction between the two modes does not involve the Rotating Wave Approximation (RWA). The Heisenberg equations of motion are solved analytically using an approximate technique and the solutions are used to measure nonclassicalities associated with the system. The nonclassicality criteria chosen in this study are experimentally measurable. The analytical solutions are matched with numerical simulations with the help of a numerical toolbox. It is evident from the time developments of the operators that nonclasities, namely squeezing and quantum entanglement are present in the system. The counting statistics for the oscillator with lower free energy and the coupled mode are shown to be sub-Poissonian for a particular set of parameters. Consequently, the system may exhibit quantum mechanical antibunching.

This article reports the radiation performance enhancement of an electrically small antenna using sub-wavelength metal strip grating, in the microwave frequency regime. The sub-wavelength grating converts the high spatial-frequency components of radiation emitted from an inductor loaded truncated-ground open coplanar antenna into a low spatial far-field spectrum. The spectral conversion results in enhanced efficiency and radiated power gain in the S-band corresponding to TE polarization. The gain of the antenna is enhanced from −9.74 dBi to 1.6 dBi for TE polarization. The prototypes are fabricated in-house and the design is validated experimentally.

Efficient and optimal energy transport is one of the present challenges in the physics of many different devices. In this context, the dynamic effective thermal diffusivity of a fluid with a non-Fourier heat conduction law is examined. Considering the simplest description for heat conduction beyond Fourier's law (the Cattaneo-Vernotte equation), an enhancement in the heat transported under oscillating conditions for both Newtonian and Maxwellian fluids may be obtained. The possible impact of such enhancement on the optimization of heat transfer processes and energy efficiency, and hence the importance of searching for fluids obeying the Cattaneo-Vernotte heat transport (specially for use in nanoscales where the effect may have an influential role) are also discussed.

A parabolic mirror is used for the first time in a wide-angle ellipsometric system to determine the parameters ψ and Δ and the thickness of SiO₂ layer naturally grown on Si crystal substrate. Collimated illuminating beam of diameter 20 mm incident on a parabolic mirror is reflected at the Si-SiO₂ system to provide wide angle of incidence. The polarization states of points in the illuminated area are determined and the data is analyzed for real-time thickness maps over the measured area of the surface. The thickness of SiO₂ layer is found as 3.02 nm with Standard deviation ±0.12 nm. Null ellipsometer is also used at different angles of incidence to check our result and nearly the same thickness value was obtained.

This work gives the description of the derived wave induced by convective diffusive flux of gradient driven diffusion. It makes use of the autonomous system of differential equations. A four compartment system is proposed for the wave produced. The diffusive flux is studied for it is inferred to facilitate transfer of by-products (metabolites) of solution-particle (efavirenz) material. The by-product wave movement is more pronounced in the initial 5 h. The initial 2.5 h indicate a period of a stretching space. The advective movement is the main generator of movement. The interaction of the advective movement's transient state with its equilibrium potential state gives rise to other movement state-dynamics.

In a broad spectrum of physics and engineering applications, transcendental equations have to be solved in order to determine their roots. Exact and explicit algebraic expression of solutions to such equations is, in general, impossible. Analytical approximate solutions to two kinds of transcendental equations with wide applications are presented. These approximate root formulas are systematically established by using the Padé approximant and show high accuracy. As an application of the proposed approximations, a highly accurate expression of the effective mass of the spring for a spring-mass system is obtained. The method described in this paper is also applied to other transcendental equations in physics and engineering applications.

Magneto-optical surface plasmon resonance (MOSPR) sensors benefit from a magneto-optic enhancement with respect to surface plasmon resonance (SPR) sensors, making these devices attractive for biosensing applications. Typical design compromises seek to balance magneto-optic effects and optical losses associated with surface plasmon waves extending to the ferromagnetic layer. Here, we demonstrate that Co/Au multilayers can yield sizeable MOSPR improvements in spite of the relative high total Co layer thickness. Co (t_Co)/Au (2 nm) multilayers, with 1.2 ≤ t_Co ≤ 1.8 nm are prepared and characterized. X-ray analysis shows that the microstructure maintains high layer periodicity and improves upon annealing. The multilayer structures were then modeled to study their SPR/MOSPR sensitivities, suggesting that the MOSPR sensitivity is enhanced by a factor of up to 3 and 4 with respect to the SPR sensitivity when the devices are operated in Air and Water media, respectively. We find that multilayers provide a particular advantage when operating the sensors in Water-based media.

The paper investigates the dynamics of entanglement and explores some geometrical characteristics of the trajectories in state space, in four-qubit Greenberger-Horne-Zeilinger (GHZ) - and W-type states, coupled to common and independent classical random telegraph noise (RTN) sources. It is shown from numerical simulations that: (i) the dynamics of entanglement depends drastically not only on the input configuration of the qubits and the presence or absence of memory effects, but also on whether the qubits are coupled to the RTN in a CE or IEs; (ii) a considerable amount of entanglement can be indefinitely trapped when the qubits are embedded in a CE; (iii) the CE configuration preserves better the entanglement initially shared between the qubits than the IEs configuration, however, for W-type states, there is a period of time and/or certain values of the purity for which, the opposite can be found. Thanks to the results obtained in our earlier works on three-qubit models, we are able to conclude that entanglement becomes more robustly protected from decay when the number of qubits of the system increases. Finally, we find that the trajectories in state space of the system quantified by the quantum Jensen Shannon divergence (QJSD) between the time-evolved states of the qubits and some reference states may be curvilinear or chaotic.

We consider a parametrically forced Bose–Einstein condensate in the combined presence of an optical lattice and harmonic oscillator potential in the mean field approach. A spatial symmetry broken Bose-condensed phase in non-inertial and inertial frame yields a stripe phase in the presence of both cubic and quintic nonlinearities. We show that the existence of such stripe phase solely depends on the interplay between the quintic nonlinearity and the lattice potential. Furthermore, we observe that a time-dependent harmonic oscillator frequency destroys such stripe ordering. A linear stability analysis of the obtained solution is performed and we found that the solution is stable. In order to gain a better understanding of the underlying physics, we compute the energy, showing nonlinear compression of the condensate in some parameter domain.

The main objective of the present work to develop Semi-empirical Method (SEM) which can provide analysis of cultivated soil-samples non-destructively. Gamma-ray transmission measurement of soil-sample provides information about its parameters such as mass attenuation coefficient, mass-density, water content and porosity. These parameters further quantify soils suitability for particular crop and irrigation system to be used for the cultivation of particular crop. Soil-samples have been collected from the cultivated soils of Punjab (India). Chemical-compositions of these samples have been measured with XRDR (x-ray Diffraction followed by Rietveld analysis). Three standard γ-ray point-isotropic sources have been used for experimental measurements of these parameters for the samples in the energy-range (59.54–1332.5 keV). A standardized self-designed computer program has been used for theoretical computations of these parameters. Good agreement between spectrometric-method (experimental) and theoretical-method (TM) have been observed with ±5% fluctuations. It is concluded that by measuring chemical composition of soil, its other parameters can be computed theoretically, thus the present methods is named as SEM. Thus, SEM is a non-destructive soil analysis (NDSA) without any loss of valuable information.

Large bandgaps with low transmission in 3D macroporous silicon photonic crystals have been proved as an interesting technology for the development of optical filters and spectroscopic MIR gas sensors. The aim of this study is the investigation of different bandgap widening methods based on multiperiodic structures for 3D macroporous silicon photonic crystals. To do so, chirped modulations and structures with different periodicity groups have been modelled and theoretically analysed by means of 3D FDTD simulations. They have revealed that by using different decreasing periodicity groups, bandgaps with null transmission and widths as high as 1800 nm, 4 times the original single periodicity photonic crystal bandgap, can be obtained. Furthermore, it has been shown that a resonant cavity with a 20% transmission can be placed in a 1 μm wide bandgap. The results open a way to use this type of structures not only for gas sensing but also for other purposes such as wide stop-band filters, selective filters or broadband mirrors.

The elasticity of networks comprised of semi-flexible polymers plays a vital role in regulating the mechanics of both intra- and extra-cellular matrices. The behaviour of this polymer scaffold will depend on the nature and density of cross-linking between constituent fibres. While modelling efforts have investigated the effects of cross-link density in biopolymer networks, this is often accompanied by changes in both the fibre density and the network structure. We investigate the elasticity of a quasi two-dimensional Mikado network of elastic rods, in which cross-link density is allowed to vary while polymer density is held constant. In particular, this model is extended by allowing constituent rods to cross without forming cross-links, while polymer density and network geometry are preserved. In doing so, the competing contributions to the shear modulus from cross-link density, mesh size, geometry and polymer density are decoupled. We find that previous scaling laws fail to capture the well-studied transition from bend- to stretch- dominated elasticity as cross-link density is varied. We identify a length scale which relates cross-link density to the transition between affine and nonaffine regimes, and which provides a collapse of simulation data curves for varying cross-link densities.

The intriguing connection between black holes' evaporation and physics of solitons is opening novel roads to finding observable phenomena. It is known from the inverse scattering transform that velocity is a fundamental parameter in solitons theory. Taking this into account, the study of Hawking radiation by a moving soliton gets a growing relevance. However, a theoretical context for the description of this phenomenon is still lacking. Here, we adopt a soliton geometrization technique to study the quantum emission of a moving soliton in a one-dimensional model. Representing a black hole by the one soliton solution of the Sine-Gordon equation, we consider Hawking emission spectra of a quantized massless scalar field on the soliton-induced metric. We study the relation between the soliton velocity and the black hole temperature. Our results address a new scenario in the detection of new physics in the quantum gravity panorama.

Johnson-Segalman fluid flow is examined in this article between two eccentrically rotating disks. Analysis of velocity and temperature profile is carried out in the presence of Hall current and non-coaxial rotation. The governing non linear momentum and energy equations of Johnson-Segalman fluid constitute a complicated system of equations corresponding to an intricate regime which are solved by using a step wise numerical algorithm (VIM). The graphical interpretations for velocity and temperature profiles have been made for various embedded parameters of interest.

We demonstrate amplitude reconstruction of a very large scene hologram recorded by means of digital holography at 10.6 microns. Infrared digital holography is characterized by a low vibration sensitivity and a large field of view with respect to the analog technique in the visible range and it is, therefore, particularly suited for outdoor remote monitoring of large scenes. However, given the typical infrared sensor sensitivities, the power density scattered back by a large irradiated scene is usually not sufficient to produce a high signal to noise ratio hologram unless very high power lasers are used. Here we show that Mid Infrared Scanning Digital Holography can solve this problem. In particular, we report on the hologram amplitude reconstruction of a 6 m × 6 m scene from a distance of 30 m in outdoor condition using a compact 60 W CO₂ laser and a microbolometric camera.

This work deals with models described by a single real scalar field in two-dimensional spacetime. The aim is to propose potentials that support massless minima and investigate the presence of kinklike structures that engender polynomial tails. The results unveil the presence of families of asymmetric solutions with energy density and linear stability that behave adequately, enhancing the importance of the analytical study. We stress that the novel topological structures which we find in this work engender long range interactions that are of current interest to statistical mechanics, dipolar quantum gases and the study of quantum information with Rydberg atoms.

This publication describes a re-analysis of previously published data on neutral carbon (C I). We used critically examined and improved values for the line energies of the absorption spectrum of molecular iodine to calibrate the transition energies of C I absorption lines originating from the 1s²2s²2p3s³P°₂ level and terminating on highly excited Rydberg states of the 1s²2s²2pnp³D₃ series. This series converges on the first excited fine-structure level of the ionic ground configuration. Additional use of improved energy values for the 1s²2s²2p3s³P°₂ level and for the fine-structure interval of the ionic ground state together with modern fitting techniques lead to a new value of the ionization energy of neutral carbon with 9 times the precision of previous work, 90 820.348(9) cm⁻¹ (equivalent to 11.260 2880(11) eV), as well as a table of predicted values for the energies of unobserved states in the series.

An optical method for storing and recovering multiple color images is presented in this paper. In the storing process, the red, green, and blue components of a color image are separated and respectively quantized. Then the three quantized components are combined as a gray image. Multiple gray images are modulated with corresponding blazed gratings and superposed in a phase-only hologram. In the recovering process, a spatial filter is used to extract all the gray images from the hologram, and the gray scales of the gray images are then converted to the pre-defined colors. The simulation shows that 206 color images can be stored in a phase-only hologram of a size of 512 by 512 pixels and reconstructed from the hologram with high fidelity.

Human dynamics and sociophysics suggest statistical models that may explain and provide us with better insight into social phenomena. Here we propose a generative model based on a stochastic differential equation that allows us to analyse the polls leading up to the UK 2016 EU referendum. After a preliminary analysis of the time series of poll results, we provide empirical evidence that the beta distribution, which is a natural choice when modelling proportions, fits the marginal distribution of this time series. We also provide evidence of the predictive power of the proposed model.

We present a study of patterns, formed in drying drops of aqueous gelatin solution containing sodium sulphate. The patterns are highly complex, consisting of a hierarchical sequence of rings which form concentric bands as well as dendritic crystalline aggregates. We try to explain the origin of the rings and the dendritic growth from them, from a simple physical approach using the advection diffusion equations. We implement a finite difference scheme in 2-dimensions to simulate the experimental results. The effect on pattern formation using different solutions are examined by variation of contact angle and diffusivity. Our model can explain the growth dynamics of a complex pattern that covers several length scales, from the nano scale of single crystals, to the micro scale of dendrites and finally rings that are of the scale of centimeters.

The effect of silver film thickness on the surface plasma resonance was investigated in the rectangular Ag-Si-SiO₂ cavity by FDTD. The resonant intensity, the quality factors and the extinction ratios, the intensity and the decay length of electric field, and the amplitude E₀ of farfield Re(E) are closely related to the silver film thickness t, especially the electric field and the magnetic field at t ≤ 5 nm. By fine tuning the thickness of silver film, this structure can be used as wave filter and good laser resonator when t ≥ 8 nm, phase regulator when t ≤ 10 nm and electromagnetic field monitor of farfield.

We study the influence of an additional uncontrolled (stray) magnetic field upon the measurement of long-range spin-spin interaction strength of two spin-1/2 valence electrons bound in two separate ions at well-defined distances from each other. This stray field, which is neither perpendicular nor parallel to the line connecting two ions, could appear due to the Earth magnetic field, or, due to the slight angular misalignment between the applied magnetic field and the line connecting two ions. It is found that the presence of the stray magnetic field plays an important role in the dynamics of the spin-states of two electrons. If neglected in the analysis, moreover, such a stray field may affect the measurement of the spin-spin interaction strength, especially at smaller inter-spin distances.

Coupled double quantum dots (c-2QD) connected to leads have been widely adopted as prototype model systems to verify interference effects on quantum transport at the nanoscale. We provide here an analytic study of the thermoelectric properties of c-2QD systems pierced by a uniform magnetic field. Fully analytic and easy-to-use expressions are derived for all the kinetic functionals of interest. Within the Green's function formalism, our results allow a simple inexpensive procedure for the theoretical description of the thermoelectric phenomena for different chemical potentials and temperatures of the reservoirs, different threading magnetic fluxes, dot energies and interdot interactions; moreover they provide an intuitive guide to parametrize the system Hamiltonian for the design of best performing realistic devices. We have found that the thermopower S can be enhanced by more than ten times and the figure of merit ZT by more than hundred times by the presence of a threading magnetic field. Most important, we show that the magnetic flux increases also the performance of the device under maximum power output conditions.

We present a unique method for solving for the Reynolds stress in turbulent canonical flows, based on the momentum balance for a control volume moving at the local mean velocity. A differential transform converts this momentum balance to a solvable form. Validations with experimental and computational data in simple geometries show quite good results. An alternate Lagrangian analytical method is offered, leading to a potential closure method for the Reynolds stress in terms of computable turbulence parameters.

The hyperfine structure in the 6p²-configuration in lead has been analysed and the results are compared with calculations. The hyperfine anomaly and improved values of the nuclear magnetic moment for four lead isotopes are obtained, using the results from the analysis. Using the the trend recommended adjustment of the nuclear magnetic moment in four isotopes is suggested. The results open up for new measurements of the hyperfine structure in unstable lead isotopes, in order to obtain improved values of the nuclear magnetic moment,extract information of the hyperfine anomaly and distribution of magnetisation in the nucleus.

Reference-frame-independent quantum key distribution (RFI-QKD) can generate secret keys with the slow drift of reference frames. However, the performance of practical RFI-QKD systems deteriorates with the increasing drift of reference frames. In this paper, we mathematically demonstrate the worst relative rotation of reference frames for practical RFI-QKD systems, and investigate the corresponding performance with optimized system parameters. Simulation results show that practical RFI-QKD systems can achieve quite good performance against the worst relative rotation of reference frames, which exhibit the feasibility of practical QKD systems with free drifting reference frames. Furthermore, we propose a universal estimation method of the secret key rate in practical RFI-QKD systems, which conforms to the nature of RFI-QKD more well than the usual estimation method.

By using the complete active space self consistent field (CASSCF) with multi-reference configuration interaction MRCI + Q method including single and double excitations with Davidson correction, the 26, 27 and 25 low-lying doublet and quartet electronic states in the representation ^2s+1Λ^(+/−) (without spin orbit interaction) of the molecules BeH, MgH and SrH have been investigated. The potential energy curves, the internuclear distance R_e, the harmonic frequency ω_e, the permanent dipole moment μ, the rotational constant B_e and the electronic transition energy with respect to the ground state T_e are calculated. Using the canonical approach the eigenvalue E_v, the rotational constant B_v and the abscissas of the turning points R_min and R_max have been calculated for the investigated electronic states. The comparison between the values of the present work and those available in the literature for several electronic states shows very good agreement.

The carrier-envelope offset (CEO) frequency stabilization of a Ti:sapphire mode-locked laser with a Fourier-transform-limited pulse width of 100 fs-scale has been successfully realized. With the home-built f-2f interferometer, the CEO beat signal has been measured with a signal-to-noise ratio (SNR) as high as 40 dB under a resolution bandwidth of 100 kHz, which means that the coherence of the octave-spanning supercontinuum (SC) is well retained, although the evaluated pulse soliton order (N ≈ 23) completely violate the previous theoretical limitation that N should be smaller than 16. Furthermore, a stabilized CEO frequency is achieved with residual phase noise suppressed to 660 mrad (integrated from 1 Hz to 100 kHz) and an Allan deviation relative to the optical carrier of 7.6 × 10⁻¹⁸ at 1 s integration time. This realization constructs a solid foundation for further generation of quantum frequency comb needed for ultra-sensitive optical timing measurement applications.

In this paper, a systematic design and analysis of thin film crystalline silicon solar cells decorated with bilayer silver nanoparticles with different particle dimensions is presented. The particles are located on the rear of the solar cell. Using numerical simulations, we showed that the light absorption is enhanced when the particle radii of the upper layer Ag NPs is less than that of the lower. Moreover, our proposed structure showed a 9.97% increase in short-circuit current density and a 9.94% increase in intergraded quantum efficiency across the solar spectrum compared with the optimized counterpart decorated with uniform Ag NPs.

We identify that a breather soliton solution for the one-dimensional non-linear Schrödinger equation, presented here, is characteristically distinct when one studies the associated space curve, specifically that this space curve is knotted. The significance of these solutions with such a non-trivial geometrical element is pre-eminent on two counts: it is a one-dimensional model wherein structures with such non-trivial geometry are unexpected, and that the nonlinear Schrödinger equation is well known to model a plethora of physical systems.

This study uses an acoustic technique to determine the surface topography for three target objects. Ultrasound is used to define the 3D surface of a wrench, the face of a British twenty-pence coin (20p) that features the profile of Queen Elizabeth II and a US five-cent coin. A single transducer is used to automatically scan the target region, in order to produce a matrix of the point-to-point reflected amplitude data. This work not only showed the surface topography of the targets as a 3D image but also scaled up the height of the particular local surface, which proves that the signal processing method can be applied to make special display treatment for the local area of interest. The experimental process and results perform an attempt method for 3D image reconstruction. Spatial resolution is important for the production of 3D images. For the three experiments, the transducer moves in 0.1 mm steps, which give tens of thousands of scanned data points within the given region. The scale of the surface topography is adjusted by recalibrating the reflected signals. The maps show the reflection coefficient for the two kinds of coins, varied from 0.74 to 0.99.