International Journal of Modern Physics B

According to the standard theory of superconductivity, the origin of superconductivity is electron pairing. The induced current by a magnetic field is calculated by the linear response to the vector potential, and the supercurrent is identified as the dissipationless flow of the paired electrons, while single electrons flow with dissipation. This supercurrent description suffers from the following serious problems: (1) it contradicts the reversible superconducting-normal phase transition in a magnetic field observed in type I superconductors; (2) the gauge invariance of the supercurrent induced by a magnetic field requires the breakdown of the global $U(1)$ gauge invariance, or the nonconservation of the particle number; and (3) the explanation of the ac Josephson effect is based on the boundary condition that is different from the real experimental one.

We will show that above problems are resolved if the supercurrent is attributed to the collective mode arising from the Berry connection for many-body wavefunctions. Problem (1) is resolved by attributing the appearance and disappearance of the supercurrent to the abrupt appearance and disappearance of topologically protected loop currents produced by the Berry connection; problem (2) is resolved by assigning the non-conserved number to that for the particle number participating in the collective mode produced by the Berry connection; and problem (3) is resolved by identifying the relevant phase in the Josephson effect is that arising from the Berry connection, and using the modified Bogoliubov transformation that conserves the particle number.

We argue that the required Berry connection arises from spin-twisting itinerant motion of electrons. For this motion to happen, the Rashba spin–orbit interaction has to be added to the Hamiltonian for superconducting systems. The collective mode from the Berry connections is stabilized by the pairing interaction that changes the number of particles participating in it; thus, the superconducting transition temperatures for some superconductors is given by the pairing energy gap formation temperature as explained in the BCS theory. The topologically protected loop currents in this case are generated as cyclotron motion of electrons that is quantized by the Berry connection even without an external magnetic field.

We also explain a way to obtain the Berry connection from spin-twisting itinerant motion of electrons for a two-dimensional model where the on-site Coulomb repulsion is large and doped holes form small polarons. In this model, the electron pairing is not required for the stabilization of the collective mode, and the supercurrent is given as topologically protected spin-vortex-induced loop currents (SVILCs).

The effects of doping with different Mo contents on the microstructure and properties of Fe36Ni Invar alloys were investigated. The results show that when 0.9 wt.% Mo and 1.8 wt.% Mo were added to Fe36Ni, the tensile strengths of the hot rolled alloys were 46 and 61 MPa higher than that of the 0 wt.% Mo sample, respectively. With an increase in Mo content from 0.9 to 1.8 wt.%, the solution temperature of the highest hardness after heat treatment increased from 800${}^{\circ }$C to 850${}^{\circ }$C, respectively. The addition of 0.9 wt.% Mo refined the average grain size from 37 to 15 $\mu$m, and an excessive amount of Mo (1.8 wt.%) did not refine the grains further. After Mo was added, the precipitates on the original grain boundaries changed into nanoprecipitates dispersed in the grain boundaries and inside the grains. Mo was present in the alloy in the form of a carbide and in solid solution, which affected the magnetic lattice effect and increased the thermal expansion coefficient of the alloy. However, upon comparing the samples doped with 0 wt.% Mo, 0.9 wt.% Mo and 1.8 wt.% Mo, it was found that the addition of 0.9 wt.% Mo not only refined the grain size and improved the mechanical properties of the alloy but also led to a low coefficient of thermal expansion (CTE) over the range from 20${}^{\circ }$C to 300${}^{\circ }$C.

A broadband and wide-angled microwave absorber based on resistive-type metamaterial has been proposed and demonstrated in the low-frequency regime of 2–8 GHz. The minimum reflection loss of the absorption peak located at 5.27 GHz is −51.41 dB. Effective bandwidth better than −10 dB reflection loss is able to achieve 2.70 GHz in the range from 3.81 GHz to 6.51 GHz. The underlying physical mechanisms of electromagnetic wave energy attenuation are illustrated in detail by means of surface current, electromagnetic field and power loss density. Furthermore, the influence of structural dimensions on the attenuation properties of the proposed resistive-type metamaterial absorber is also investigated. More importantly, the designed resistive-type metamaterial absorber could operate well with incident angles changing from 0${}^{\circ }$ to 60${}^{\circ }$ under the transverse electric (TE) and transverse magnetic (TM) waves. Research results will be capable of providing guidance for the design and preparation of broadband microwave absorbing materials at low frequencies.

Pedestrian-car interweaving is a prominent problem in old residential communities in Chinese cities. To achieve a better pedestrian-car separation to create a safe and comfortable living environment in old residential communities, this paper investigated the mechanism of the flows of pedestrians and cars on a road network inside an old residential community. A method for calculating the flows of pedestrians and cars was proposed to identify the road segments or nodes where the pedestrian flows are interlaced or intersected with the vehicle flows. This method was applied to the estimation of the traffic in the Wangyuehu Community of Changsha City, China. The estimated distribution of community network traffic and pedestrian-car interweaving sites was consistent with the actual situation.

By the potential method, it was determined that regardless of the nature of the liquid, the surface tension coefficient is determined by $\sigma =2q\frac{(T_K-T)}{(T_K+T)}$. In this expression, $q$ is the specific heat of the surface formation, $T_k$ is the critical temperature. According to our approach, the specific heat of the surface formation (SHS) also depends on temperature: $q=q_m+\alpha \cdot (T-T_m)$ ($q_m$ — the specific heat of the surface formation at the mealting temperature, $\alpha$ — thermal coefficent of SHS). In this research work, the temperature dependence of the surface tension coefficient was calculated for seven dissimilar liquids. It was revealed that the calculated values of $\sigma$ are in satisfactory agreement with the available experimental values.

In this article, we have discussed the analytical treatment of perturbed chiral nonlinear Schrödinger equation with the help of our newly developed method extended modified auxiliary equation mapping method (EMAEMM). By using this newly proposed technique we have found some quite general and new variety of exact traveling wave solutions, which are collecting some kind of semi half bright, dark, bright, semi half dark, doubly periodic, combined, periodic, half hark, and half bright via three parametric values, which is the primary key point of difference of our technique. These results are highly applicable to develop new theories of quantum mechanics, biomedical problems, soliton dynamics, plasma physics, nuclear physics, optical physics, fluid dynamics, biomedical problems, electromagnetism, industrial studies, mathematical physics, and in many other natural and physical sciences. For detailed physical dynamical representation of our results we have shown them with graphs in different dimensions using Mathematica 10.4 to get complete understanding in a more efficient manner to observe the behavior of different new dynamical shapes of solutions.

The activation function of human neurons is usually regarded as a monotonically differentiable function with upper and lower bounds. Considering the mathematical properties of the hyperbolic tangent function, the activation function can be simulated by a hyperbolic tangent function. In this paper, a fraction-order novel hyperbolic-type memristor Hopfield neuron network (FHMHNN) based on three neurons is proposed, which is achieved using a hyperbolic-type memristor synapse-coupled weight to substitute a coupling-connection weight. The equilibrium points and stability analysis of the FHMHNN are discussed in detail, and the types of generating attractor are determined. Furthermore, the coexisting behaviors of the FHMHNN are described by bifurcation diagram, phase diagram and time diagram. Numerical results show that the FHMHN presents complex dynamical transition, evolving from periodic to chaotic and finally to a stable point with the changes of the memristor coupling weight and inner parameter of the hyperbolic-type memristor. It should be emphasized that the coexisting oscillation behaviors of the FHMHNN under different initial conditions will appear for different inner parameters of the memristor. Theoretical analysis and numerical simulation are basically consistent, revealing that the FHMHNN has the globally coexisting behavior of the asymmetric attractors.

We investigate the oscillating dynamics in a ring of network of nonlocally delay-coupled fractional-order Stuart-Landau oscillators. It is concluded that with the increasing of coupling range, the structures of death islands go from richness to simplistic, nevertheless, the area of amplitude death (AD) state is expanded along coupling delay and coupling strength directions. The increased coupling range can prompt the coupled systems with low frequency to occur AD. When system size varies, the area of death islands changes periodically, and the linear function relationship between periodic length and coupling range can be deduced. Thus, one can modulate the oscillating dynamics by adjusting the relationship between coupling range and system size. Furthermore, the results of numerical simulations are consistent with theoretical analysis.

We have investigated the sub-cycle correlated electron dynamics of nonsequential double-ionization (NSDI) of Ar atom by few-cycle counter-rotating two-color circularly polarized (TCCP) laser fields using a three-dimensional classical ensemble model. Numerical results indicate that NSDI probability sensitively depends on the relative phase of the two components and achieves its maximum at the relative phase 0.7$\pi$. Back analysis of NSDI trajectories shows that the return angle of the electron is closely related to the relative phase of the two components and can continuously be controlled by changing the relative phase. Furthermore, the relative phase also influences the relative contribution of recollision-induced direct ionization (RII) and recollision-induced excitation with subsequent field ionization (RESI) to NSDI and the final emitted direction of the electrons.

In this paper, a $(2+1)$-dimensional modified Heisenberg ferromagnetic system, which appears in the biological pattern formation and in the motion of magnetization vector of the isotropic ferromagnet, is being investigated with the aim of exploring its similarity solutions. With the aid of Lie symmetry analysis, this system of partial differential equations has been reduced to a new system of ordinary differential equations, which brings an analytical solution of the main system. Infinitesimal generators, commutator table, and the group-invariant solutions have been carried out by using Lie symmetry approach. Moreover, conservation laws of the above mentioned system have been obtained by utilizing the new conservation theorem proposed by Ibragimov. By applying this analysis, the obtained results might be helpful to understand the physical structure of this model and show the authenticity and effectiveness of the proposed method.

In this paper, a novel approach is presented for the first time to increase the energy gap of Si-based material by doping carbon atoms into Si-based material structures. The structural electronic properties and mechanical properties of ${\mathrm{\text{Si}}}_{1-x}{\mathrm{\text{C}}}_x$ ($x=0.05$, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4) are investigated using a first-principles calculation method. Bandgaps of the ${\mathrm{\text{Si}}}_{1-x}{\mathrm{\text{C}}}_x$ shells were found to have, respectively, quadratic relationships with the Carbon content $(x)$. Meanwhile, the electronic bandgap of Si-based material can be increased by 0.334 eV due to the carbon substitutions. The optimal structure is ${\mathrm{\text{Si}}}_{0.7}{\mathrm{\text{C}}}_{0.3}$ and the elastic constants and phono calculations reveal that ${\mathrm{\text{Si}}}_{0.7}{\mathrm{\text{C}}}_{0.3}$ is mechanically and dynamically stable. Finally, two different heavy doped ${\mathrm{\text{Si}}}_{0.7}{\mathrm{\text{C}}}_{0.3}$ have been investigated and the results indicate that the $p$-type and $n$-type doped ${\mathrm{\text{Si}}}_{0.7}{\mathrm{\text{C}}}_{0.3}$ do produce shallow levels. This study can be a theoretical guidance to improve the bandgap of Si-based semiconductors. In addition, ${\mathrm{\text{Si}}}_{0.7}{\mathrm{\text{C}}}_{0.3}$ show superior bandgap and material properties enabling ${\mathrm{\text{Si}}}_{0.7}{\mathrm{\text{C}}}_{0.3}$ power device operation at higher temperatures, voltages than current Si-based power semiconductor device.

Link prediction based on traditional models have attracted many interests recently. Among all models, the ones based on topological similarity have achieved great success. However, researchers pay more attention to links, but less to endpoint influence. After profound investigation, we find that the synthesis of degree and H-index plays an important role in modeling endpoint influence. So, in this paper, we propose link prediction models based on weighted synthetical influence, exploring the role of H-index and degree in endpoint influence measurement. Experiments on 12 real-world networks show that the proposed models can provide higher accuracy.

To explore the directional transmission channel that can efficiently transport acoustic energy, we analyzed the local state characteristics of a mirror symmetric interface (MSI) in an artificial periodic structure. It was found that in a one-dimensional (1D) waveguide structure with alternating high- and low-resonant units, the acoustic energy can be localized at the symmetric interface. The result can be extended to a 2D waveguide array, implying that the acoustic energy can be transported efficiently along the interface. In addition, to improve the robustness of the acoustic system, we designed a graphene-like periodic structure based on a hexagonal lattice. By breaking the six-fold rotation symmetry of the structure, the topological interface was constructed, and the backscattering of the acoustic wave was effectively suppressed, enabling the acoustic wave energy to be transported with low reflection even in the curved waveguide. These results may provide a new direction for the realization of high-tech applications such as micromotor and 2D integrated communication.

In this research, a particular attention has been given on the fractional Fokas-Lenells equation via Atangana-Baleanu derivative operator that describe the propagation of short pulses in optical fibers. The integrability properties has been investigated while using the modified Khater method that we present in details. As a result, number of new soliton solutions are obtained along with constraints on some parameters that are introduced accordingly. For further details about our obtained solutions, some distinct types of solutions have been illustrated to explain more physical and dynamical behavior of the short wave pulses in the optical fibers.