Realization of corner and helical edge states in topologically trivial band gap by twig edge

The twig edge states in graphene-like structures are viewed as the fourth states complementary to their zigzag, bearded, and armchair counterparts. In this work, we study a rod-in-plasma system in honeycomb lattice with twig edges under external magnetic fields and lattice scaling and show that twig edge states can exist in different phases of the system, such as quantum Hall phase, quantum spin Hall phase and insulating phase. The twig edge states in the quantum Hall phase exhibit robust one-way transmission property immune to backscattering and thus provide a novel avenue for solving the plasma communication blackout problem. Moreover, we demonstrate that corner and edge states can exist within the trivial band gap of the insulating phase by modulating the on-site potential of the twig edges. Especially, helical edge states with the unique feature of pseudospin-momentum locking that could be exited by chiral sources are demonstrated at the twig edges within the trivial band gap. Our results show that many topological-like behaviors of electromagnetic waves are not necessarily tied to the exact topology of the systems and the twig edges and interface engineering can bring new opportunities for more flexible manipulation of electromagnetic waves

The simulation of terahertz waves transmission in the arc plasma

The diagnostic of high-density hot plasma is a challenging task due to its high temperature and electron density. Arc plasma is one of the typical hot density plasmas, and its diagnosis is the key to develop its new applications. In this paper, the temperature and density distributions of welding plasmas with different discharge currents are numerically simulated based on a Tungsten Inert Gas Arc Welding model, and the electron density distributions are calculated. Then propagation properties of broadband terahertz (THz) waves in the modeling arc jets are calculated by the finite difference time domain method. These results not only provide a preliminary theoretical guidance for in-depth understanding the problems of blackout in re-entry communication, but also develop a new idea for the terahertz diagnostic of plasma with high density

Transition from periodic to chaotic oscillations in a planar gas discharge-semiconductor system

The work studies the transition from periodic to chaotic oscillations in a dc-driven planar gas discharge with a high-ohmic electrode. The applied voltage and resistance of the semiconductor layer act as control parameters. The oscillations occur in the subnormal discharge regime. The bifurcation diagram and Lorenz map characterizing transition of this system to chaos through period-doubling bifurcations are obtained. Numerical models employed are based on the drift-diffusion theory of gas discharges. The effect of two modelling approaches, namely the 'simple' fluid model and the more detailed 'extended' fluid model, is considered. The calculations showed that the results obtained by these two approaches are different in quantitative terms, however, qualitatively similar in terms of the dynamic behavior of the system as a function of the control parameters

Parametric study of coaxial dielectric barrier discharge in atmospheric pressure argon

A parametric study of the characteristics of coaxial dielectric barrier discharge sustained in atmospheric pressure argon is carried out. The numerical model is based on the drift-diffusion theory of gas discharges. The integral characteristics of the discharge, such as the root mean square of the discharge current, the period average dissipated power, and the efficiency of the power deposition, are explored in the parameter space spanned by the voltage amplitude and frequency of the applied AC field, the barrier dielectric constant, and the gas gap width

Analysis of parameters of coaxial dielectric barrier discharges in argon flow at atmospheric pressure

This work deals with the numerical and experimental investigation of atmospheric pressure dielectric barrier discharges (DBDs). In the experiment, the current and voltage of DBD sustained in an argon flow in coaxial discharge cell are measured. Numerical models are based on the drift-diffusion theory of gas discharges. Different modelling approaches, where the electron kinetics is determined on the basis of the Maxwellian electron energy distribution function (EEDF), vs models with more realistic EEDF obtained from the solution of the electron Boltzmann equation are implemented. The effect of energy loss due to heating of the gas is considered

Microwave diagnostics of pulsed atmospheric discharge with electrolytic electrode and long‐lived luminous formation in its afterglow

Abstract The Gatchina discharge phenomenon holds significant promise as a laboratory model for simulating ball lightning. However, crucial aspects concerning the plasma components of the resulting afterglow remain unresolved. Notably, the measurement of the electron density, a critical parameter, has not been fully achieved thus far. In this study, microwave diagnostics and video recording were employed during a pulsed Gatchina discharge, along with synchronous measurement of discharge current and voltage. Distinct antennas were positioned at different heights to enable separate diagnosis of the discharge and the ensuing long‐lived afterglow. The findings revealed that during the active phase of the Gatchina discharge, the plasma density was substantial enough to cause reflection of an electromagnetic wave with a frequency of 20 GHz from this highly conductive object. In the afterglow, the signal experienced only a moderate weakening of 10–20 percent, facilitating the determination of the time dependence of average electron density during the afterglow's passage between the two antennas. These measurements verified the unusually slow plasma decay in the afterglow of the Gatchina discharge, suggesting the potential significance of chemi‐ionisation processes involving long‐lived (metastable) particles