Modern Physics Letters B

It is proved that a nontrivial compact dynamical system with asymptotic average shadowing property (AASP) displays uniformly distributional chaos or distributional chaos in a sequence. Moreover, distributional chaos in a system with AASP can be uniform and dense in the measure center, that is, there is an uncountable uniformly distributionally scrambled set consisting of such points that the orbit closure of every point contains the measure center. As a corollary, the similar results hold for the system with almost specification property.

The structural, electronic, elastic and phonon properties of the cubic spinels AB₂O₄ (A = Ge, Si; B = Mg, Zn, Cd) compounds at zero pressure are investigated via density functional theory (DFT) using the Perdew–Burke–Ernzerhof (PBE) exchange–correlation functional. It has been shown that the predicted values of the structural parameters ($a_0$ and $u$), bulk modulus $(B)$, elastic constants $(C_{ij})$, shear modulus $G$ and $B/G$ ratio are in good agreement with the previously reported results. The phonon dispersion curves of the AB₂O₄ (A = Ge, Si; B = Mg, Zn, Cd) are calculated for the first time using the direct method. The estimated phonon spectra indicate that GeMg₂O₄, GeZn₂O₄, GeCd₂O₄, SiMg₂O₄ and SiZn₂O₄ are dynamically stable in the cubic spinel structure.

Bound states degenerated in energy (and differing in parity) may form in one-dimensional quantum mechanics if the potential is unbounded from below. We focus on symmetric potential and present quasi-exactly solvable (QES) model based on WKB method. The application of this method is limited on slow-changing potentials. We consider the overlap integral of WKB wave functions ${\mathrm{\Psi }}_1$ and ${\mathrm{\Psi }}_2$ which correspond to energies $E_1$ and $E_2$, and by setting $E_1\to E_2$, we determine the type of spectrum depending on parameter $\lambda$ which arises from this method. For finite value $\lambda$, we show that the entire spectrum will consist of degenerated bound states.

Fe-doped In₂O₃ nanotubes were successfully synthesized by electrospinning technique followed by subsequent heat treatment. The as-prepared samples appeared as an apparently open-end one-dimensional (1D) and tubular-like morphology with the diameter of approximately 150 nm and the wall thickness about 20 nm. The diffraction peak of the obtained nanotubes shifts toward bigger angle direction with the increase of the Fe content. Comparing to the In₂O₃ nanotubes, the Fe-doped In₂O₃ nanotubes exhibit better sensing characteristics toward ethanol gases, including higher sensing response, lower operating temperature and higher selectivity. Enhanced sensing properties are attributed to 1D hollow nanostructures and the role of doping Fe element.

The basic idea of a microscopic understanding of thermodynamics is to derive its main features from a microscopic probability distribution. In such a vein, we investigate the thermal statistics of quasi-probabilities’s semiclassical analogs in phase space for the important case of quadratic Hamiltonians, focusing attention in the three more important instances, i.e. those of Wigner, $P$- and Husimi distributions. Introduction of an effective temperature permits one to obtain a unified thermodynamic description that encompasses and unifies the three different quasi-probability distributions. This unified description turns out to be classical.

We studied the crystal structure of perovskite BiAlO₃ using ab initio density functional theory (DFT) calculations. Using the atomic positions given by the previous literature, we were able to create a lattice structure using visualization software Material Studio. Such sophisticated structure is found in rhombohedral perovskite system with space group with R3c (#161) and lattice parameter of $a=b=c=5.338\mathrm{\text{Å}}$, bond angle of $\alpha =\beta =\gamma =60^{\circ }$, while treating the exchange–correlation potential with the local density approximations (LDA) method. The calculations were performed to investigate the electronic, optical, elastic and phonon properties.

For the first time, the electronic and optical properties of the quaternary Be${}_x$Mg${}_y$Zn${}_{1-(x+y)}$Se alloy have been investigated using first-principles calculations within the framework of density functional theory (DFT). Variations in the direct band gap with the change in $x$ and $y$ compositions show agreement with the experimental measurements. Evaluation of the dielectric function and refractive index reveals the optical activity in the visible and ultraviolet energy regions.

The transition phenomenon of few-cycle-pulse optical solitons from a pure modified Korteweg–de Vries (mKdV) to a pure sine-Gordon regime can be described by the nonautonomous mKdV–sinh-Gordon equation with time-dependent coefficients. Based on the Bell polynomials, Hirota method and symbolic computation, bilinear forms and soliton solutions for this equation are obtained. Bäcklund transformations (BTs) in both the binary Bell polynomial and bilinear forms are obtained. By virtue of the BTs and Ablowitz–Kaup–Newell–Segur system, Lax pair and infinitely many conservation laws for this equation are derived as well.

In this paper, a novel optical absorber that is flexible in size for fabrication and unique properties is studied numerically by aid of finite difference in time domain (FDTD) algorithm. The structure consists of three layers based on the metal–dielectric–metal design scheme. The middle layer is a dielectric in which the electronic and magnetic resonance energy dissipates. The bottom side is a metallic plane and the top layer is a hexagonal prism array. We also investigate the influence of the structure parameters on the absorbance and the absorption wavelength. The results show that a perfect absorber can be designed, and the number of the absorption peaks varies from two to three for the different radius of circumcircle of the hexagonal prism ranging from 280 nm to 400 nm. Meanwhile, position of the first absorption peak is nearly unchanged. This unique feature may be a significant advantage and possesses great potential applications such as biosensing and photovoltaic. Additionally, position and amplitude of the first absorption peak is constant for broad incident angles. The absorption is insensitive to the polarization of the incident beam due to the highly symmetric structure.

The asymmetrical nested metamaterial, composed of two split-ring resonators (SRRs) and two embedded gallium arsenide (GaAs) islands placed in the two SRRs, has been elaborately designed on quartz substrate. Its tunable and switchable resonances at terahertz (THz) frequencies are numerically demonstrated here based on different conductivities of GaAs, which can be transformed from semiconductor to metallic state through appropriate optical excitation. Without photoexcitation, our designed metamaterial has three resonance peaks in the range of monitored frequency range, and they are located at 0.813, 1.269 and 1.722 THz, respectively. As the conductivity of the two GaAs islands increases, different new resonances appear and constantly strengthen. Finally, four new resonant points are generated, at 0.432, 0.948, 1.578 and 1.875 THz, respectively. At the same time, the metamaterial structure is changed from the original nested mode to a new integral mode. Applying reversible changing conductivity of semiconductor to push the conversion of resonance, this asymmetrical nested design provides a new instance in application and development of additional THz devices.

This paper studies the mechanical properties of polyethylene (PE)–Single-walled carbon nanotube (SWCNT) complexes by using density functional theory (DFT). At the PBE/SVP level, the Young’s modulus of the complexes is obtained as a function of PE content. It is established that, with increasing number of PE chains attached to the SWCNTs, the Young’s modulus monotonically decreases. The density of states (DOS) results show that no orbital hybridization exists between the PE chains and nanotubes. The results of this work are of importance for the design of composite materials employing SWCNTs.

The system of Kohn–Sham equations is solved self-consistently for the two-dimensional, spatially separated electrons and holes. We find the series of magic numbers for the total angular momentum of the electrons and holes in a strong magnetic field. The change of the angular momentum of the charge carriers is shown to lead to the persistent current oscillations.