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One of the important challenges that graphene must overcome before it can legitimately declare its irreplaceable position among the fields of plasmonic materials is to achieve efficiently coupling to external light. In this paper, we demonstrate an effective solution to this problem by exciting localized surface plasmon polaritons (SPPs) on graphene-coated nanowire arrays (GCNAs). These SPPs are analyzed by introducing a universal scaling law that considerably simplifies the understanding of these modes. Meanwhile, numerical experiments are carried out to demonstrate the theoretical analysis of plasmon excitations. The excited SPPs permit the control through both geometrical and physical properties. The proposed structure can be used as a tunable optical filter, a highly sensitive refractive index sensor, and other plasmonic modulation devices. [ABSTRACT FROM AUTHOR]

By using the Green's function method, we have investigated spin Hall conductance (SHC) in a four terminal quantum spin Hall insulator. The results show that the intrinsic spin orbit coupling in a HgTe/CdTe hetero-structure interface naturally leads to separate probability distributions for the two spins in coordinate space, which leads to the spin Hall effect in our proposed device. We also find that the SHC of bulk states exhibits an oscillatory behavior as a function of the device width and persists at a broad device width. In addition, we calculate the effects of disorder on the SHC of the bulk states of non-trivial and trivial topology. The results indicate that the spin up and spin down conductances show different degrees of suppression by disorder; thus the SHC could be significantly enhanced by the disorder. This kind of property has a great value to practical applications. [ABSTRACT FROM AUTHOR]

Spin dependent transport in one-dimensional (1D) three-terminal rings is investigated in the presence of the Rashba spin-orbit coupling (RSOC). We focus on zero-conductance resonances and spin polarizations. For these purposes, the transmission functions are derived analytically. The total conductances are analyzed in the complex energy plane with a focus on the zero-pole structure characteristic of transmission (anti)resonances. The spin polarizations in symmetrically and asymmetrically coupled three-terminal rings are studied as a function of the incident electron energy. It is found that in the absence of the RSOC there are three kinds of conductance zeros. In the presence of the RSOC, the zeros of the first and the third kinds are lifted, while some of the second kind persist. The lifting of the conductance zeros is related to the breaking of the spin-reversal symmetry, and the lifted conductance zeros evolve into spin polarization zeros. [ABSTRACT FROM AUTHOR]

The effect of an ac electric field on quantum transport properties in a system of three quantum dots, two of which are connected in parallel, while the third is coupled to one of the other two, is investigated theoretically. Based on the Keldysh nonequilibrium Green's function method, the spin-dependent current, occupation number, and spin accumulation can be obtained in our model. An external magnetic flux, Rashba spin-orbit-coupling (SOC), and intradot Coulomb interactions are considered. The magnitude of the spin-dependent average current and the positions of the photon assisted tunneling (PAT) peaks can be accurately controlled and manipulated by simply varying the strength of the coupling and the frequency of the ac field. A particularly interesting result is the observation of a new kind of PAT peak and a multiple-PAT effect that can be generated and controlled by the coupling between the quantum dots. In addition, the spin occupation number and spin accumulation can be well controlled by the Rashba SOC and the magnetic flux. [ABSTRACT FROM AUTHOR]

Considering the difference of energy bands in graphene and silicene, we put forward a new model of the graphene-silicene-graphene (GSG) heterojunction. In the GSG, we study the valley polarization properties in a zigzag nanoribbon in the presence of an external electric field. We find the energy range associated with the bulk gap of silicene has a valley polarization more than 95%. Under the protection of the topological edge states of the silicene, the valley polarization remains even the small non-magnetic disorder is introduced. These results have certain practical significance in applications for future valley valve. [ABSTRACT FROM AUTHOR]

A relative permeability model for transient two-phase flow in fractal porous media is derived based on the fractal characteristics of pore size distribution and the assumption that porous media consists of capillary bundles. The functions in this model are tortuosity fractal dimension, pore fractal dimension, and maximum and minimum pore diameters. Every parameter has clear physical meaning without the use of empirical constants. Good agreement between model predictions and experimental data is obtained, the sensitive parameters that influence the relative permeability are specified and their effects on relative permeability are discussed. [ABSTRACT FROM AUTHOR]

The transport properties in graphene-based asymmetric double velocity well (Fermi velocity inside the well less than that outside the well) and electrostatic well structures are investigated using the transfer matrix method. The results show that quantum beats occur in the oscillations of the conductance for asymmetric double velocity wells. The beating effect can also be found in asymmetric double electrostatic wells, but only if the widths of the two wells are different. The beat frequency for the asymmetric double well is exactly equal to the frequency difference between the oscillation rates in two isolated single wells with the same structures as the individual wells in the double well structure. A qualitative interpretation is proposed based on the fact that the resonant levels depend upon the sizes of the quantum wells. The beating behavior can provide a new way to identify the symmetry of double well structures. [ABSTRACT FROM AUTHOR]

Using the one-dimensional effective potential method, we theoretically study the properties of an exciton in vertically coupled quantum dots (VCQDs) under the influence of an applied magnetic field. The ground state transition energies of the heavy-hole exciton are calculated in a single quantum dot and in VCQDs, respectively. Our results are in good agreement with those of experiments. In symmetrical VCQDs, the entanglement of the exciton state monotonously increases with increasing barrier width, and can even attain the value of the maximally entangled state. When the symmetry of the VCQDs is broken, the entanglement of the exciton state almost entirely breaks down under the combined influences of tunneling and the Coulomb interactions. [ABSTRACT FROM AUTHOR]

We have investigated the effect of the coupling of localized surface plasmon (LSP) on the transmission properties of a compound structure with metallic particle and hole arrays. It is found that the variation in longitudinal interval G between particle and hole arrays leads to the shift in transmission peak and the new transmission peak, which are due to the change in coupling strength of LSP modes and the formation of coaxial guide mode, respectively. The lateral displacement Lx (parallel to the polarization direction of incident light) results in the splitting of transmission peak, originating from the variation in coupling manner of LSP modes, while the lateral displacement Ly (perpendicular to the polarization direction of incident light) causes the reduction and redshift in transmission peak. [ABSTRACT FROM AUTHOR]

The properties of a hydrogenic impurity in a parabolic GaAs quantum-well wire in the presence of the magnetic field are investigated using the finite-difference method within the quasi-one-dimensional effective potential model. The magnetic effects on the energies and binding energies of the ground and lowest excited states of a hydrogenic impurity in a parabolic GaAs quantum-well wire are studied for various parabolic potentials. The calculated results indicate that the interplay of the spatial confinement and the magnetic confinement of electrons in the quantum-well wires leads to complicated binding energies of the hydrogenic impurity, and high magnetic fields significantly increase the binding energies of the hydrogenic impurity in the case of weak spatial confinement. [ABSTRACT FROM AUTHOR]

In this paper, we aim to introduce a new form of the (3+1)-dimensional generalized Kadomtsev-Petviashvili equation for the long waves of small amplitude with slow dependence on the transverse coordinate. By using the Hirota’s bilinear form and the extended homoclinic test approach, new exact periodic solitary-wave solutions for the new (3+1)-dimensional generalized Kadomtsev-Petviashvili equation are presented. Moreover, the properties and characteristics for these new exact periodic solitary-wave solutions are discussed with some figures. [ABSTRACT FROM AUTHOR]

An electrically pumped wavelength-tunable InGaN quantum dot (QD) based microcavity (MC) lighter emitter with a large tuning range of 129 nm was demonstrated. The multi-mode emission spectrum was tuned by injected current from 564 nm (yellow-green) to 435 nm (violet). The MC light emitter is featured with a double dielectric distributed Bragg reflector structure and a copper substrate fabricated using substrate transfer and laser lift off techniques. By utilizing an InGaN QD active layer with a tunable broad emission spectrum and a Fabry-Pérot cavity which allows multi-longitudinal mode resonating, the emission spectrum could be tuned among several particular cavity modes, which are decided by the gain enhancement factor. In addition, both the enhancement and suppression of MC emission modes caused by the gain enhancement factor were observed in a single MC device. As the first electrically driven III-V nitride semiconductor based tunable MC light emitter with a tuning range of 129 nm, the device is promising for applications such as in wide-gamut compact displays and projectors. [ABSTRACT FROM AUTHOR]

Core-shell nanostructures exhibit unique optical and catalytic properties that are dependent on their morphology and composition. In this paper, a general and facile way was developed to prepare Au-nanoisland-coated Au nanorods with porous structures. Pt nanodots were first formed on Au nanorods by using a simple successive reduction growth. Then, the island growth mode of Pt on the Au rod was employed to guide the growth behavior of Au-nanoisland. Because of the high dielectric sensitivity of the Au nanostructures, tiny changes in the shell structure can be readily seen from absorption spectra and electromagnetic field enhancement. Simulations of absorption spectra and the electromagnetic field enhancement using the finite difference time domain (FDTD) method and taking into account the real shapes of the core-shell nanostructures were reported. The accuracy and validity of the FDTD method were verified. The results presented here indicated that surface plasmon resonances of these core-shell metallic nanostructures produce strong effects in both the near- and far-field optical responses. [ABSTRACT FROM AUTHOR]

The Korteweg-de Vries (KdV)-type models have been shown to describe many important physical situations such as fluid flows, plasma physics, and solid state physics. In this paper, a new (2þ1)- dimensional KdV equation is discussed. Based on the Hirota's bilinear form and a generalized three-wave approach, we obtain new exact solutions for the new (2þ1)-dimensional KdV equation. With the help of symbolic computation, the properties for some new solutions are presented with some figures. [ABSTRACT FROM AUTHOR]

The ongoing precision measurement of the gravitational constant G at our group is performed by using two different kinds of methods: time-of-swing method (ToS) and angular acceleration feedback method. In the two methods, the stainless steel spheres are employed as source masses, and the position stability of the spheres is an important parameter, which make suitable mounts for supporting the spheres needed extremely. In this paper, an upgraded three-point mount is introduced and tested in detail. Experimental results show that, for the sphere supported by the three-point mount used in the ToS method, the repeatability, the temperature influence, and the vibration influence are all less than 0.1 μm (about 2 ppm for the value of G). For the sphere supported by the three-point mount used in the AAF method, similar results are obtained, the largest change of the sphere's position is about 0.6 μm, introduced by a temperature change of 1 °C, which also results in an uncertainty of 2 ppm for the value of G. [ABSTRACT FROM AUTHOR]

Employing the Keldysh Nonequilibrium Green's function method, we investigate time-dependent transport through a topological superconductor with Majorana bound states in the presence of a high frequency microwave field. It is found that Majorana bound states driven by photon-assisted tunneling can absorb(emit) photons and the resulting photon-assisted tunneling side band peaks can split the Majorana bound state that then appears at non-zero bias. This splitting breaks from the current opinion that Majorana bound states appear only at zero bias and thus provides a new experimental method for detecting Majorana bound states in the Non-zero-energy mode. We not only demonstrate that the photon-assisted tunneling side band peaks are due to Non-zero-energy Majorana bound states, but also that the height of the photon-assisted tunneling side band peaks is related to the intensity of the microwave field. It is further shown that the time-varying conductance induced by the Majorana bound states shows negative values for a certain period of time, which corresponds to a manifestation of the phase coherent time-varying behavior in mesoscopic systems. [ABSTRACT FROM AUTHOR]

The electroluminescence (EL) spectra of blue-green light emitting InGaN/GaN multiple quantum well (MQW) structures grown via metal-organic chemical vapor deposition are investigated. With increasing In content in InGaN well layers, the peak energy redshifts, the emission intensity reduces and the inhomogeneous broadening of the luminescence band increases. In addition, it is found that the EL spectra shrink with increasing injection current at low excitation condition, which may be ascribed to both Coulomb screening of polarization field and carrier transferring from shallower localization states to the deeper ones, while at high currents the state-filling effect in all localization states may become significant and lead to a broadening of EL spectra. However, surprisingly, for the MQW sample with much higher In content, the EL spectral bandwidth can be almost unchanged with increasing current at the high current range, since a large number of carriers may be captured by the nonradiative recombination centers distributed outside the localized potential traps and the state-filling effect in the localization states is suppressed. [ABSTRACT FROM AUTHOR]

By using two-dimensional particle-in-cell simulations, we demonstrate high-flux dense positrons generation by irradiating an ultra-intense laser pulse onto a tapered hollow target. By using a laser with an intensity of 4 ×1023W/cm², it is shown that the Breit-Wheeler process dominates the positron production during the laser-target interaction and a positron beam with a total number >1015 is obtained, which is increased by five orders of magnitude than in the previous work at the same laser intensity. Due to the focusing effect of the transverse electric fields formed in the hollow cone wall, the divergence angle of the positron beam effectively decreases to ~15° with an effective temperature of ~674 MeV. When the laser intensity is doubled, both the positron flux (>1016) and temperature (963 MeV) increase, while the divergence angle gets smaller (~13°). The obtained high-flux low-divergence positron beam may have diverse applications in science, medicine, and engineering. [ABSTRACT FROM AUTHOR]

Due to the high-Q fused silica fiber's extreme sensitivity to temperature change, the period estimation of torsion pendulum with high precision depends on the effective correction of the thermoelastic effect. In the measurement of G with the time-of-swing method, we analyze the complex relation between temperature and the pendulum's period and propose a developed method to find the shear thermoelasticity coefficient as well as isolate the influence of temperature on period alone. The result shows that the shear thermoelasticity coefficient is 101(2) x 10-6/°C, the resultant correction to Δ(ω²) is 9.16(0.18) ppm, and the relative uncertainty to G is less than 1 ppm. [ABSTRACT FROM AUTHOR]

A scheme for enhancing the electron injection charge in a laser-driven bubble acceleration is proposed. In this scheme, a thin foil target is placed in front of a gas target. Upon interaction with an ultra-intense laser pulse, the foil emits electrons with large longitudinal momenta, allowing them to be trapped into the transmitted shaped laser-excited bubble in the gaseous plasma target. Twodimensional particle-in-cell simulation is used to demonstrate this scheme, and an electron beam with a total electron number of 4.21 × 108 μm-1 can be produced, which is twice the number of electrons produced without the foil. Such scheme may be widely used for applications that require high electron yields such as positron and gamma ray generation from relativistic electron beams interacting with solid targets. [ABSTRACT FROM AUTHOR]

Images formed by an underwater object from light rays refracted in the sagittal and tangential planes are located at different positions for an oblique viewing position. The overlapping of these two images from the observer's perspective will thus prevent the image-splitting astigmatism from being directly observable. In this work, we present a heuristic method to experimentally visualize the astigmatism. A point light source is used as an underwater object and the emerging wave front is recorded using a Shack-Hartmann wave-front sensor. The wave front is found to deform from a circular paraboloid to an elliptic paraboloid as the viewing position changes from normal to oblique. Using geometric optics, we derive an analytical expression for the image position as a function of the rotating angle of an arm used to carry the wave-front sensor in our experimental setup. The measured results are seen to be in good agreement with the theoretical predictions. [ABSTRACT FROM AUTHOR]

We propose and numerically analyze a terahertz tunable plasmonic directional coupler which is composed of a thin metal film with a nanoscale slit, dielectric grating, a graphene sheet, and a dielectric substrate. The slit is employed to generate surface plasmon polaritons (SPPs), and the metal-dielectric grating-graphene-dielectric constructs a Bragg reflector, whose bandgap can be tuned over a wide frequency range by a small change in the Fermi energy level of graphene. As a graphene-based Bragg reflector is formed on one side of the slit, the structure enables SPP waves to be unidirectionally excited on the other side of the slit due to SPP interference, and the SPP waves in the Bragg reflector can be efficiently switched on and off by tuning the graphene's Fermi energy level. By introducing two optimized graphene-based Bragg reflectors into opposite sides of the slit, SPP waves can be guided to different Bragg reflectors at different Fermi energy levels, thus achieving a tunable bidirectional coupler. [ABSTRACT FROM AUTHOR]

Agonist binding of A2A adenosine receptor (A2AAR) shows protective effects against inflammatory and immune. Efforts are exerted in understanding the general mechanism and developing A2AAR selectively binding agonists. Using molecular dynamics (MD) simulations, we have studied the interactions between A2AAR and its agonist (adenosine), and analyzed the induced dynamic behaviors of the receptor. Key residues interacting with adenosine are identified: A632:61, I662:64, V843:32, L853:33, T883:36, F1685:29, M1775:38, L2496:51, H2506:52, and N2536:55 interacting with adenosine with affinities larger than 0.5 kcal/mol. Moreover, no interaction between adenosine and L1675:28 is observed, which supports our previous findings that L1675:28 is an antagonist specific binding reside. The dynamic behaviors of agonist bound A2AAR are found to be different from apo-A2AAR in three typical functional switches: (i) tight "ionic lock" forms in adenosine-A2AAR, but it is in equilibrium between formation and breakage in apo-A2AAR; (ii) the rotamer toggle switch", T883:36/F2426:44/W2466:48, adopted different rotameric conformations in adenosine-A2AAR and apo-A2AAR; (iii) adenosine-A2AAR has a flexible intracellular loop 2 (IC2) and α-helical IC3, while apo-A2AAR preferred α-helical IC2 and flexible IC3. Our results indicate that agonist binding induced different conformational rearrangements of these characteristic functional switches in adenosine-A2AAR and apo-A2AAR. [ABSTRACT FROM AUTHOR]

Since the fouling-releasing ability of silicone elastomers increased as their modulus decreases, we designed and prepared composites with embedded tiny NaCl crytals that were soluble after their immersion in water, resulting in water-filled porous elastomers. The scanning electron microscope images confirmed such a designed water-filling porous structure. The existence of many micro-drops of water in these specially designed elastomers decreased the shear storage modulus and increased the loss factors. The decrease of shear modulus plays a leading role here and is directly related to a lower critical peeling-offstress of a pseudo-barnacle on them. Therefore, such a novel preparation with cheap salts instead of an expensive silicone provides a better way to make fouling-release paints with a lower modulus, a lower critical peeling-offstress and a better fouling-release property without a signficant decrease of the cross-linking density. [ABSTRACT FROM AUTHOR]

Surface acceleration of fast electrons in intense laser-plasma interaction is investigated by using subwavelength grating targets. The fast electron beam emitted along the target surface was enhanced by more than three times relative to that by using planar target. The total number of the fast electrons ejected from the front surface of grating target was two times higher than that of planar target. The method to enhance the surface acceleration of fast electrons may have several applications such as in ion acceleration and the experiment of high energy density physics. [ABSTRACT FROM AUTHOR]

Hot electron emission from subwavelength grating targets irradiated by a 60 fs short-pulse laser was investigated at moderate intensities in excess of 1015 W/cm2. Collimated hot electron jets with a divergence angle as small as 5° were observed at the specular reflection direction when the laser beam was incident at the resonance angle for surface plasmon excitation. When the incident angle, which departs from the resonant angle, is increased, the collimated hot electron jet remains near the specular reflection direction, but its intensity attenuates gradually. At the same time, the number of the hot electrons with very large spreading angle emitting along the target normal direction increases with the incident angle. [ABSTRACT FROM AUTHOR]

Describing plasma physics, cluster physics, and geophysical fluid dynamics, a generalized variable-coefficient two-dimensional Korteweg–de Vries (GVCKdV) model is hereby under investigation. In this paper, an extended-variable-coefficient homogeneous balance method with symbolic computation is used to obtain an auto-Bäcklund transformation, some rational solutions, and new soliton-type solutions for the GVCKdV model. The solutions of the well-known cylindrical Kadomtsev-Petviashvili equation can be recovered as special cases of the results obtained here. [ABSTRACT FROM AUTHOR]

We study the spin polarization and the spin accumulation in an Aharonov–Bohm ring structure, in which a quantum dot (QD) array is side-coupled to one arm of the ring and the Rashba spin-orbit interaction exists in the other. The device can be as a spin switch by decreasing the tunneling coupling between the QD array and the ring. Moreover, we find that the spin polarization and the spin accumulation in the QD are affected by the number of the QDs in the QD array and can be controlled by the strength of the Rashba spin-orbit interaction and the bias on the Aharonov–Bohm ring. [ABSTRACT FROM AUTHOR]

We propose a quantum dot (QD) array device which contains a bridge coupling between two leads. Due to the quantum interference and the Rashba spin-orbit interaction, the spin of the electrons through the device is polarized. Moreover, we find odd-even parity oscillations of spin polarization of the electrons through the system. We study the spin accumulations in every QD and find that there is difference between the spin accumulations of the QDs directly and indirectly coupling to leads. These results demonstrate that the bridge coupling is a flexible and feasible way to manipulate the electron spin of the QD array. [ABSTRACT FROM AUTHOR]

Examines the high frequency electro-optic modulation of chiral smectic C* ferroelectric liquid crystal (FLC). Contribution on inter- and intramolecular interactions for electro-optic effects; Nominal response time for the molecular reorientation of FLC mixtures.

A letter to the editor is presented in response to the article "Graphene metamaterial for optical reflection modulation" by W. Zhu, I. D. Rukhlenko, and M. Premaratne in 2013 issue.