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Vortex patterns of dust particles have been observed in a magnetized dusty plasma system. The formation mechanism of two-dimensional (2D) vortex patterns has been investigated by analysing the forces acting on dust particles and molecular dynamics (MD) simulations in a 2D confined magnetized dusty plasma. It has been found that with a weak confining electric field and a strong magnetic field, the particles' trajectories will form a vortex shape. The simulation results agree with our experimental observations. In our experiments, vortex patterns can be induced via circular rotation of particles by changing the rf (radio-frequency) power in a magnetized dusty plasma.

In this paper, the structural and single-particle motive properties of a two-dimensional dusty plasmas are investigated numerically by molecular dynamics simulation within the framework of a dissipative Yukawa model. The pair correlation function, the mean square displacement, the static structure factor, and the bond angle correlation function characterizing the structural properties, and the velocity autocorrelation function with Fourier spectrum function characterizing the single-particle motion have been calculated for different values of coupling constant Gamma and viscous damping constant v(f). The results show that the system will coagulate quickly with increasing viscous damping constant and coupling constant, and the critical value of friction parameter decreases with increasing the coupling constant in the system.

The behaviour of defect particles in a two-dimensional (2D) confined dusty plasma system is investigated by molecular dynamics (MD) simulations. The mean square displacement (MSD) and the pair correlation function g(r) are used to characterize the structural and dynamical properties of the system. The influences of the number and the charge (mass) of the defect particles on the system configurations are simulated. All the defect particles with charges (masses) larger than the normal particles have the trend to move towards the system centre. The moving speed of the defect particles towards the centre increases with the increasing number and charge (mass) of defect particles and with the system temperature.

Multi-species charged-particles interacting with each other by a competing short-range attraction and long-range repulsion potential confined in a quadratic trap are studied with molecular dynamics simulations. It is found that particles with similar mass-to-charge ratio tend to populate a common shell, whose location depends on the particle mass-to-charge ratio, and that the greater the latter is, the closer the particles to the centre of the trap are. This rule for the ground-state configuration is independent of the total particle and species numbers in the system.

The structure and single-particle motion of a two-dimensional dusty plasma have been investigated. Pair correlation function, mean square displacement, velocity autocorrelation function, and the corresponding spectrum function have been computed by molecular dynamical simulation. The results show that the coagulation of a two-dimensional dusty plasma system is strongly affected by particle density and temperature, which are discussed in details.

The structure and phase transition of a two-dimensional (2D) dusty plasma have been investigated in detail by molecular dynamics simulation. Pair correlation function, static structure factor, mean square displacement and bond angle correlation function have been calculated to characterize the structural properties. The variation of internal energy, shear modulus, particle trajectories and structural properties with temperature has been monitored to study the phase transition of the 2D dusty plasma system. The simulation results are in favour of a two-step continuous transition for this kind of plasma.

Collective motion modes existing in a two-dimensional Yukawa system are investigated by molecular dynamics simulation. The dispersion relations of transverse and longitudinal lattice waves obtained for hexagonal lattice are in agreement with the theoretical results. The negative dispersion of the parallel longitudinal wave is demonstrated by the simulation, and is explained by a physical model.

Like the spin in spintronics, the valley index in graphene can be viewed as a new carrier of information, which is useful for designing modern electronic devices. Recently, we have applied the concept of valleytronics to photonic graphene, revealed valley-dependent beam splitting effect and realized pseudomagnetic field. The pseudomagnetic field enables a novel manipulation of photons. In this paper, the photonic analogy of valley Hall effect in uniaxially distorted photonic graphene is investigated. It is found that photons in two valleys are subjected to pseudomagnetic fields that are equal in strength but opposite in sign. With the increasing of distortion, the valley Hall effect becomes stronger. In addition, it is found that the photonic valley Hall effect can still be maintained under the influence of loss, although the beam intensity decreases. The photonic analogy of valley Hall effect induced by pseudomagnetic field in uniaxially distorted photonic graphene may be very useful for controlling the flow of light in future valley-polarized devices.

The behaviors of electrons as they move under the influence of mirror magnetic field and non-uniform electric field in a positive column of helium radio frequency gas discharge are studied by Monte Carlo simulation. Some types of collisions (elastic, excitation and ionization collisions) are considered. Graphs showing how the electron density, electron energy, electron current density, collision rate and the electron-scattering angular distribution are affected by the mirror magnetic field are presented. The results indicate that the mirror magnetic field can control the electron transport behavior in the positive column. In the presence of the mirror magnetic field, the electrons are restricted in the middle part of the positive column, and the electron density is greatly increased. The electron collision rate and the electron current density are enhanced in the middle region, and the electron-scattering angles are extended by the mirror magnetic fields. These results are in good agreement with experimental results.

A Monte Carlo simulation technique has been used to model the electron transport behavior, especially the electron density and energy distributions under the influence of a mirror magnetic field and a uniform electric field in a positive column of helium direct current (DC) gas discharge. Graphs showing the electron density and energy distributions, and the percentage of electrons that reach the wall and the end of the positive column are presented. The results indicate that the mirror magnetic field can control the electron transport behavior in the positive column which are in good agreement with experimental results.

A two-dimensional dusty plasma lattice in an rf discharge was observed. The structural and dynamical properties were analysed by computing pair correlation function, static structure factor, bond-orientational correlation function and mean square displacement. The bond-orientational correlation function was found to fit into the law of r-0.25, and the mean square displacement experienced ``ballistic'', ``subdiffusive'' and ``diffusive'' regimes, both of which together with the other parameters indicate that the two-dimensional dusty plasma stayed at a state between liquid and solid.

Recently, Chan and his collaborators reported that a crossing point of bands can be achieved at the Brillouin zone center in two-dimensional (2D) dielectric photonic crystals (PhCs) by accidental degeneracy of modes. At the crossing point, the accidental threefold degeneracy of modes generates a Dirac cone and an additional flat band (longitudinal mode) intersecting the Dirac cone. This is different from that of the Dirac point at the corner of the hexagonal Brillouin zone in which only Dirac cone exists. As a result, the crossing point at the Brillouin zone center is called a Dirac-like point. If the accidental degeneracy occurs by a monopole mode and two dipolar modes, the dielectric PhCs can be mapped to a zero-refractive-index system in which the effective permittivity and permeability are zero at the Dirac-like point from the effective medium theory. According to the Maxwell equations, if the permittivity and permeability are zero, the optical longitudinal modes can exist, in additional to the well-known transverse modes. The additional flat band at the Dirac-like point is closely connected with the longitudinal mode. For a homogeneous zero-index material (ZIM), the flat band is dispersionless and the longitudinal mode cannot couple with the external light. But in a finite-sized PhC, there is always some spatial dispersion, so the flat band is not perfectly dispersionless when it is away from the zone center. Therefore, if the wave source is a Gaussian beam with non-zero k-parallel components, the longitudinal mode can be excited. And the effective wavelength of ZIM is extremely large, leading to many scattering properties. However, in a PhC which behaves as if it had a zero refractive index, it is very interesting to show how the longitudinal mode influences the wave propagations in the PhC when the longitudinal mode is excited. In this paper, the effect of longitudinal mode on the transmission properties near the Dirac-like point of PhCs is investigated by numerical simulation. The alumina dielectric rods can be moved randomly in the structure to result in the disorder of the structure. Our results show that the transmission properties at the Dirac-like point are very different from those near the Dirac-like point, when the longitudinal mode is excited. At the Dirac-like point, the transmittance decreases with increasing disorder, as a result of the influence of the longitudinal mode, which is similar to the one in the pass band. Above the Dirac-like point without the disturbance of longitudinal mode, the transmittance is insensitive to the disorder in the structure, so that the structure may mimic a near-zero index materials and have a large effective wavelength. These results may further improve the understanding about the optical longitudinal mode and the zero refractive material.

According to the technology of LC-load transmission lines photonic quantum well structures are fabricated. Two kinds of structures are act as quantum well. While the left-handed materials works as well, the number of resonance modes increase with the thickness of left-handed materials. Compared with the condition of photonic crystals work as well, the left-handed materials act as well has the advantage of smaller size and adjusting. Experimental results are consistent with theory.

Structures and dynamics of two-dimensional dust lattices with and without Coulomb molecules in plasmas are investigated. The experimental results show that the lattices have the crystal-like hexagonal structures, i.e. most particles have six nearest-neighboring particles. However, the lattice points can be occupied by the individual particles or by a pair of particles called Coulomb molecules. The pair correlation function is used to compare the structures between the lattices with or without the Coulomb molecules. In the experiments, the Coulomb molecules can also decompose and recombine with another individual particle to form a new molecule.

This paper computes the rotational energy levels of the HCO 2A'-X2A' transition, especially, the higher values of the rotational quantum numbers NKaKc and Ka, with the rotational constants which are obtained via B3LYP method with 6–311G basis set, and the results show that the calculated frequencies using the computed vibration-rotation energy levels are in reasonable agreement with the data from the experiment. Meanwhile, the line intensities of HCO are first reported, the results are of significance for the studying HCO.