Chinese Journal of Physics最新文献

A proposed model delves into the resonant enhancement of third harmonic generation (THG) by a short-pulse laser inside nanoclustered plasma under the influence of density ripple. An intense chirped laser pulse incident on a clustered plasma of argon gas displaces the electrons of the medium and produces a restoring force. This force is considered to vary nonlinearly with electron displacement, leading to the anharmonic response of the electron clouds of the cluster. The nonlinear current at the third harmonic frequency arises from the perturbation of the electron density of the cluster by the ponderomotive force exerted on them by the incident laser pulse. Applying ripple in cluster density and electron density of surrounding plasma enables the phase-matching criteria for THG to be satisfied, which leads to enhanced harmonic output. An anharmonic structure of clusters exhibits strong optical nonlinearities, resulting in the plasmon resonance broadening and producing harmonics with greater efficiency. Numerical analysis shows that the chirp parameter of the laser pulse and ripple on cluster density enhance system nonlinearity causing the generation of a third harmonic of enhanced amplitude. The study explores how different factors such as laser intensity, cluster size, ripple parameter, chirp parameter, and electron excursion influence the efficiency of THG.

The delay of information transmission is an inherent factor of the nervous systems, which has great influences on their collective dynamic behaviors. In this paper, we constructed a ring neural network using FitzHugh-Nagumo (FHN) neuron model as the network node and memristive synapses as the connection mode. Our primary focus was on investigating the effects of time delay and coupling strength on the firing frequency of neurons. Simulation results revealed that the frequency chimera state could be induced in the neural network with appropriate time delay, which is a new type of chimera state characterized by firing frequency rather than traditional membrane potential. By adjusting the time delay properly, the neural network can also display multi-cluster frequency chimera states that coexisted with various incoherent regions and coherent regions. Meanwhile, we exhibit that initial value and coupling strength could have great influences on the effects of time delay on inducing frequency chimera state of the nervous systems.

Voigt and Maxwell models are popularly used to model viscoelastic materials’ property. They are often presented in form of fractional relaxation equations. In order to describe rich viscoelasticity, a general Caputo derivative is introduced in fractional modeling. Then this work studies attractivity and asymptotic stability of the Caputo fractional relaxation equation with general memory effects. Firstly, the considered problem is transformed into an integral equation. A mapping and an attractive set are constructed. Furthermore, the existence of fixed points on the attractive set are investigated by using fixed point theorems. Finally, the effectiveness and convenience of the stability theory are verified through two numerical examples.

In this work, we analyze the new generalized soliton solutions for the nonlinear partial differential equations with a novel symbolic bilinear technique. The proposed approach constructs the soliton solutions depending on the arbitrary parameters, which generalizes the soliton solutions with these additional parameters. Examining phase shifts and their dependence on the parameters influences how solitons collide, merge, or pass through each other, which is essential for the nonlinear analysis of solitons. Using the proposed technique, we examine the well-known (1＋1)-dimensional Korteweg–de Vries (KdV) and (2＋1)-dimensional Kadomtsev–Petviashvili (KP) equations with a comparative analysis of soliton solutions in the Hirota technique. We construct the generalized solitons solutions for both examined equations up to the third order, providing a better understanding of formed solitons with arbitrary parameter choices. The Cole-Hopf transformations are used to construct the bilinear form in the auxiliary function using Hirota’s $D$-operators for both investigated KdV and KP equations It discusses the phase shift depending on parameters and compares it to the phase shift in Hirota’s soliton solutions. We utilize Mathematica, a computer algebra system, to obtain the generalized solitons and analyze the dynamic behavior of the obtained solutions by finding the values for the parameters and the relationships among them. Solitons are localized waves that appear in different fields of nonlinear sciences, such as oceanography, plasmas, fluid mechanics, water engineering, optical fibers, and other sciences.

Bi₂Se₃ thin films with various thicknesses of 44, 94, 190 QL (1 QL = 0.955 nm) were epitaxially grown on InP (111) substrates using a Bi₂Se₈ target and pulsed laser deposition. All the Bi₂Se₃ thin films exhibited highly c-axis preferred orientation and well in-plane orientation with six-fold symmetric diffraction patterns of Bi₂Se₃{015} facets. The films had a clean and smooth surface with triangular step-and-terrace pyramid features and a small average roughness R_a ≤ 1.47 nm. The hardness and Young's modulus of a 190 QL-thick epitaxial Bi₂Se₃ film were found to be 2.1 ± 0.1 GPa and 58.6 ± 4.1 GPa, respectively. The Bi₂Se₃ thin films exhibited the typical two-dimensional weak antilocalization magnetoresistance (2D WAL MR) in a low magnetic field regime (B ± 0.5T). Meanwhile, they presented a parabola-like MR behavior for 190-QL-thick film, and linear MR for the thinner films at a high B field regime (B ≥ 3 T). The MR results suggest the presence of 2D topological surface states together with a dominant bulk state in the Bi₂Se₃ films. Furthermore, we observed two gigahertz acoustic phonon modes at 24.04 ± 2.05 GHz and 48.11 ± 2.02 GHz in the Bi₂Se₃ films induced by ultrafast laser pulses.

We derive a solution of a quantum corrected charged AdS black hole surrounded by perfect fluid dark matter (PFDM). The thermodynamic quantities and the modified first law of thermodynamics are obtained by considering the black hole mass as chemical enthalpy rather than energy. A first order phase transition (small to large black holes) is recognized from the swallowtail in the Gibbs free energy $G$ versus Hawking temperature $T_H$ graph. The black hole exhibits the characteristic “standard liquid/gas behavior” of van der Waals fluids on the $P-V$ graph. By further studying the heat capacity of the black hole, we identify a second order phase transition at the event horizons $x_1$ and $x_2$, respectively. Thus, we demonstrate that a quantum corrected charged AdS black hole surrounded by PFDM can be studied for its thermodynamic stability and phase transition from the perspective of black hole chemistry.