Imbert–Fedorov shifts of a Gaussian beam reflected from uniaxially anisotropic chiral media

We study the Imbert–Fedorov (IF) shifts of a reflected Gaussian beam from uniaxially anisotropic chiral media (UACM), where the chirality appears only in one direction and the host medium is a uniaxial crystal or an electric plasma. The numerical results are presented for three kinds of UACM, respectively. It is found that the IF shifts are closely related to the propagation properties of the two eigenwaves in the UACM. In general, when either of the eigenwaves is totally reflected, the IF shifts can change abruptly near the critical angle. The cross-polarized reflection coefficient has a greater effect on the spatial IF (SIF) shift than on the angular IF (AIF) shift, and the sign of the AIF shift depends mainly on that of the difference between the co-polarized reflectivity. By designing artificially the electromagnetic parameters of the UACM, we can control the IF shifts and acquire their more abundant properties.     

Electron–hole transition in a spherical quantum dot confined at the center of a cylindrical nano-wire: Comparison of isotropic and anisotropic effective mass

Electronic structure of an InAs spherical quantum dot placed at the center of a GaAs cylindrical nano-wire is investigated. The Schrodinger equation within the effective mass approximation is solved and the energy eigenvalues and transition energies are calculated as a function of quantum dot and nano-wire radii using the finite element method. The two types of heavy holes, hhI and hhII, with isotropic and anisotropic effective masses are considered, respectively. The effect of spherical and nano-wire confining potentials, the size of the dot and the nano-wire on ground and first excited state energies of the electron, heavy hole I and heavy hole II are investigated. The results show that the electron and heavy holes energies decrease as the dot and the nano-wire radii increase. The emitted wavelength of transitions between el-hhI and el-hhII are also calculated and compared. The results show that the anisotropy of the effective mass has great effect on the emitted wavelength.     

Comprehensive study of the vapour–liquid coexistence of the truncated and shifted Lennard–Jones fluid including planar and spherical interface properties

Vapour–liquid equilibria of the Lennard–Jones potential, truncated and shifted at 2.5σ, are studied using molecular dynamics simulations, an attractive option for studying inhomogeneous systems. Comprehensive simulation data are reported for three cases: no interface, a planar interface, and a spherical interface between the coexisting phases, covering a wide range of temperatures. Spherical droplets are also studied for a range of radii between 5 and 16σ. The size dependence of the surface tension, based on the Irving–Kirkwood pressure tensor, and other properties is quantified for spherical interfaces. All simulation results are correlated with a consistent set of empirical equations. A comparison with the results of other authors as well as with experimental data for noble gases and methane is also presented.     

Accelerated expansion of an anisotropic Brans–Dicke cosmology from nonlinear derivative interaction and Gauss–Bonnet invariant

The study of Brans–Dicke cosmology has attracted considerable attention in the recent years since it explains most of the important features of the progress of the universe. We discuss in this letter a homogeneous and anisotropic cosmological model in the framework of Brans–Dicke theory including together a non-linear derivative interaction which appears in theory with the Galilean shift symmetry, a Gauss–Bonnet invariant motivated from heterotic string theory which plays an important role in numerous alternatives cosmological frameworks, two scalar fields and their interactions to fit easier with universe history expansion. Several particular cases are studied and the properties related to scaling solutions and asymptotic behaviour are discussed in some details.     

Critical behavior of a stochastic anisotropic Bak–Sneppen model

In this paper we present our study on the critical behavior of a stochastic anisotropic Bak–Sneppen (saBS) model, in which a parameter α is introduced to describe the interaction strength among nearest species. We estimate the threshold fitness f _c and the critical exponent τ _r by numerically integrating a master equation for the distribution of avalanche spatial sizes. Other critical exponents are then evaluated from previously known scaling relations. The numerical results are in good agreement with the counterparts yielded by the Monte Carlo simulations. Our results indicate that all saBS models with nonzero interaction strength exhibit self-organized criticality, and fall into the same universality class, by sharing the universal critical exponents.     

Non-Markovianity of a qubit coupled with an isotropic Lipkin–Meshkov–Glick bath

We study the non-Markovianity of the single qubit system coupled with an isotropic Lipkin–Meshkov–Glick(LMG)model by an effective method proposed by Breuer et al.(Breuer H P and Piilo J 2009 Europhys. Lett. 85 5004). It is discovered that the non-Markovianity is concerned with the quantum phase transitions(QPTs). In the open system, we present that the strong coupling inside the bath and the strong interaction between the system and bath can enhance the degree of non-Markovianity. Moreover, the non-Markovianity is stronger and more sensitive for the bath in the symmetric phase than the symmetry broken phase.     

Reflection–refraction of attenuated waves at the interface between a thermo-poroelastic medium and a thermoelastic medium

Phenomenon of reflection and refraction is considered at the plane interface between a thermoelastic medium and thermo-poroelastic medium. Both the media are isotropic and behave dissipative to wave propagation. Incident wave in thermo-poroelastic medium is considered inhomogeneous with deviation allowed between the directions of propagation and maximum attenuation. For this incidence, four attenuated waves reflect back in thermo-poroelastic medium and three waves refract to the continuing thermoelastic medium. Each of these reflected/refracted waves is inhomogeneous and propagates with a phase shift. The propagation characteristics (velocity, attenuation, inhomogeneity, phase shift, amplitude, energy) of reflected and refracted waves are calculated as functions of propagation direction and inhomogeneity of the incident wave. Variations in these propagation characteristics with the incident direction are illustrated through a numerical example.     

Nonlocal Nambu–Jona-Lasinio model and chiral chemical potential

We derive the critical temperature in a nonlocal Nambu–Jona-Lasinio model with the presence of a chiral chemical potential. The model we consider uses a form factor derived from recent studies of the gluon propagator in Yang–Mills theory and has the property to fit in excellent way the form factor arising from the instanton liquid picture for the vacuum of the theory. Nambu–Jona-Lasinio model is derived form quantum chromodynamics providing all the constants of the theory without any need for fits. We show that the critical temperature in this case always exists and increases as the square of the chiral chemical potential. The expression we obtain for the critical temperature depends on the mass gap that naturally arises from Yang–Mills theory at low-energy as also confirmed by lattice computations.     

Enhanced chiral response from the Fabry–Perot cavity coupled meta-surfaces

The circular dichroism(CD) signal of a two-dimensional(2D) chiral meta-surface is usually weak, where the difference between the transmitted(or reflected) right and left circular polarization is barely small. We present a general method to enhance the reflective CD spectrum, by adding a layer of reflective film behind the meta-surface. The light passes through the chiral meta-surface and propagates towards the reflector, where it is reflected back and further interacts with the chiral meta-surface. The light is reflected back and forth between these two layers, forming a Fabry–Perot type resonance,which interacts with the localized surface plasmonic resonance(LSPR) mode and greatly enhances the CD signal of the light wave leaving the meta-surface. We numerically calculate the CD enhancing effect of an L-shaped chiral meta-surface on a gold film in the visible range. Compared with the single layer meta-surface, the L-shaped chiral meta-surface has a CD maximum that is dramatically increased to 1. The analysis of reflection efficiency reveals that our design can be used to realize a reflective circular polarizer. Corresponding mode analysis shows that the huge CD originates from the hybrid mode comprised of FP mode and LSPR. Our results provide a general approach to enhancing the CD signal of a chiral meta-surface and can be used in areas like biosensing, circular polarizer, integrated photonics, etc.     

Quantum state transfer via a hybrid solid–optomechanical interface

We propose a scheme to implement quantum state transfer between two distant quantum nodes via a hybrid solid–optomechanical interface. The quantum state is encoded on the native superconducting qubit, and transferred to the microwave photon, then the optical photon successively, which afterwards is transmitted to the remote node by cavity leaking,and finally the quantum state is transferred to the remote superconducting qubit. The high efficiency of the state transfer is achieved by controllable Gaussian pulses sequence and numerically demonstrated with theoretically feasible parameters.Our scheme has the potential to implement unified quantum computing–communication–computing, and high fidelity of the microwave–optics–microwave transfer process of the quantum state.     

Goos–Hänchen shifts of a light beam reflected from the interface of colloidal ferrofluids

Controllable Goos–Hänchen shift of a light beam reflected from the colloidal ferrofluids is investigated by using the stationary-phase method. It is found that the Goos–Hänchen shift can be easily controlled by the local H_e factor and the volume factor. Using this scheme, the peak value, the peak position and the width of the Goos–Hänchen shift can all be controlled by adjusting the external magnetic field for a fixed configuration, which also provides a possibility for obtaining larger negative Goos–Hänchen shift by changing the external controlling field. Our results have potential applications in optical devices.     

Anomalous dielectric behavior in the nematic and isotropic phases of a strongly polar–weakly polar binary system

We report permittivity studies in the isotropic liquid and anisotropic liquid crystalline (nematic or N) phases of a binary system, in which one component has molecules with a strongly polar longitudinal group, and the other has a weakly polar transverse group. The dielectric constant in the isotropic phase as well as its anisotropy in the N phase show, surprisingly, an anomalous non-monotonic dependence with concentration having a peak-like behavior for 10.2 mol% concentration of the weakly polar constituent. The transition between the two phases, being weakly first order, exhibits pretransitional effects signifying the appearance of the N-like regions in the isotropic phase. The coordinates of the maximum point of the convex shaped temperature-dependence of the dielectric constant in the isotropic phase, characteristic of strongly polar systems, also exhibit a non-monotonic dependence with concentration. Possible causes for these observations are discussed.     

Magnetic properties of Nd–Fe–B system anisotropic HDDR powder made from segregated master ingots

In order to examine the possibility of applying the HDDR process to segregated master ingots, Nd–Fe–B system HDDR powders were made from ingots with different levels of homogeneity, and their structures and magnetic properties were evaluated in detail. HDDR powders made from segregated as-cast ingots displayed anisotropy and large coercivity. They had a nearly homogeneous Nd₂Fe₁₄B phase, although some large areas with α-Fe and Nd-rich regions of 30 μm in size were present after the HD process. With increasing in the homogeneity level of the master ingots, the anisotropy of HDDR-processed powders decreased and their coercivity increased. In addition, an intermediate Ar treatment was applied between the HD and DR processes to improve the magnetic properties. As a result, the effect of the IA treatment was clearly confirmed, and good magnetic properties of B_r=1.23 T, H_cJ=848 kA/m and (BH)_max=238 kJ/m³ were obtained.     

Electromagnetic field quantization and input–output relation for anisotropic magnetodielectric metamaterial

A phenomenological quantization of electromagnetic field is introduced in the presence of the anisotropic magnetodielectric metamaterial.For a single layer structure with the anisotropic metamaterial,input–output relations of quantized radiation are derived using the Green-function approach.Based on these relations,the reflectance of the linearly polarized wave through this structure is calculated.The results show that different resonant peaks of reflectance appear for different polarized waves and indicate the use of the anisotropic metamaterial as a reflector for a certain polarized wave.Furthermore it is found that such a structure can realize the resonant gap with the increase of the thickness.Finally the effects of the absorption are considered and we find that the above properties do not change with the introduction of the absorption.     

Exciton–polariton formation at room temperature in a planar ZnO resonator structure

We show the dispersion of exciton–polaritons in an all oxide planar resonator structure. A quasi-bulk ZnO film acts as active medium and as cavity. The mirrors are made of Bragg reflectors consisting of ZrO₂ and MgO layers. Despite a limited structural perfection, we have observed a giant energy splitting of the exciton–polariton branches of about 78 meV at maximum using reflectivity and photoluminescence measurements.     

Sonochemiluminescence observation and acoustic detection of cavitation induced by pulsed HIFU at a tissue–fluid interface

The aim of this study is to investigate the mechanism of the erosion process induced by 1.2 MHz pulsed high-intensity focused ultrasound (pulsed HIFU). By using Sonochemiluminescence (SCL) photograph, the initiation and maintenance of active cavitation were observed. In order to understand the role of both inertial cavitation and stable cavitation, a passive cavitation detection (PCD) transducer was used. Since the exposure variables of HIFU are important in the controlled ultrasound tissue erosion, the influence of pulse length (PL) and duty cycle (DC, T_on:T_off) has been examined. The results of tissue hole, SCL observation and acoustic detection revealed that the erosion was highly efficient for shorter PL. For higher DCs, the area of SCL increased with increasing PL. For lower DCs, the area of SCL increased with increasing PL from 10 to 20 μs and then kept constant. For all PLs, the intensity of SCL decreased with lower DC. For all DCs, the intensity of SCL per unit area (the ratio of SCL intensity to SCL area) also decreased with increasing PL from 10 to 80 μs, which suggested that the higher the intensity of SCL is, the higher the efficiency of tissue erosion is. At DC of 1:10, the position of the maximum pixel in SCL pictures was distant from the tissue–fluid interface with the increasing PL because of shielding effect. By the comparison of inertial cavitation dose (ICD) and the stable cavitation dose (SCD), the mechanisms associated with inertial cavitation are very likely to be the key factor of the erosion process.     

Large lateral shift in a prism–waveguide system with uniaxially anisotropic metamaterial

We study the lateral shifts of reflected light beams in a prism–waveguide system with uniaxially anisotropic metamaterial including lossless and lossy system. The conditions for appearance of large lateral shift are deduced in a lossless system and the expression of lateral shift in a lossy system is derived. Simulation results illustrate the influence of imaginary part of every parameter in the prism–waveguide system on lateral shift. The anisotropy of metamaterial brings us more flexibility in designing new style photonic devices, such as sensors with high sensitivity based on accurate control of constructive parameters of metamaterial.     

Relationship between characteristic lengths and effective Saffman length in colloidal monolayers near a water–oil interface

The hydrodynamic interactions(HIs) in colloidal monolayers are strongly influenced by the boundary conditions and can be directly described in terms of the cross-correlated diffusion of the colloid particles. In this work, we experimentally measured the cross-correlated diffusion in colloidal monolayers near a water–oil interface. The characteristic lengths of the system were obtained by introducing an effective Saffman length. The characteristic lengths of a particle monolayer near a water–oil interface were found to be anisotropic in the longitudinal and transverse directions. From these characteristic lengths, the master curves of cross-correlated diffusion are obtained, which universally describe the HIs near a liquid–liquid interface.