Rong-An Tang

Stability of oblique modulation of dust-acoustic waves in a warm dusty plasma with dust charge variation

With the consideration of the dust charge variation, the oblique modulational instability of the dust-acoustic waves in an unmagnetized warm dust plasma is studied. A nonlinear Schrodinger equation governing the slow modulation of the wave amplitude is derived. The effect of the dust temperature, the dust charge variation, and the constituents of the dust grains, electrons, and ions on the oblique modulational instability of the dust-acoustic wave is presented. It is found that the dust temperature, the dust charge variation, and the constituents of the dust grains, electrons, and ions would modify the oblique modulational instability domain in the k–θ plane significantly.

Nonthermal electrons and warm ions effects on oblique modulation of ion-acoustic waves

By using the standard reductive perturbation technique, a nonlinear Schrodinger equation is derived to study the instability of oblique modulation of finite amplitude ion-acoustic waves in an unmagnetized plasma consisting of warm adiabatic ions and nonthermal electrons. The effects of nonthermally distributed electrons on the modulational instability and the solitary structures are investigated. It is found that the presence of nonthermal electrons significantly changes the domain of the modulational instability in the k–θ plane.

Terahertz generation by beating two Langmuir waves in a warm and collisional plasma

Terahertz (THz) radiation generated by beating of two Langmuir waves in a warm and collisional plasma is discussed theoretically. The critical angle between the two Langmuir waves and the critical wave-length (wave vector) of Langmuir waves for generating THz radiation are obtained analytically. Furthermore, the maximum radiation energy is obtained. We find that the critical angle, the critical wave-length, and the generated radiation energy strongly depend on plasma temperature and wave-length of the Langmuir waves. That is, the THz radiation generated by beating of two Langmuir waves in a warm and collisional plasma can be controlled by adjusting the plasma temperature and the Langmuir wave-length.

Periodic waves in ultrarelativistic inhomogeneous electron-positron-ion plasma

The nonlinear interaction of ultrarelativistic intense electromagnetic/electrostatic waves and homogeneous/inhomogeneous electron-positron-ion (e-p-i) plasma are investigated. Starting from the relativistic fluid-Maxwell model, we show that the system of the governing equations can be reduced to two modified canonical equations with inhomogeneity effect. It is found that periodic wave solutions can exist in both homogeneous and inhomogeneous e-p-i plasma. However, periodic solutions can exist in inhomogeneous e-p-i plasma only when the positron density is above a critical value. The critical positron density for exciting the periodic waves strongly depends on both the inhomogeneity nature and the phase velocity of the wave. Furthermore, the topology structure of the phase space is simplified and only circular solutions can exist when the positron density is high enough.

Faraday instability and Faraday patterns in a superfluid Fermi gas

With the consideration of the coupling between the transverse width and the longitudinal density, the parametric excitations related to Faraday waves in a cigar-shaped superfluid Fermi gas are studied. A Mathieu equation is obtained, and it is demonstrated firstly that the excited actual 3D Faraday pattern is the combination of the longitudinal Faraday density wave and the corresponding transverse width fluctuation in the longitudinal direction. The Faraday instability growth index and the kinematic equations of the Faraday density wave and the width fluctuation along the Bose–Einstein condensate (BEC)–Bardeen–Cooper–Schrieffer (BCS) crossover are also given for the first time. It is found that the 3D Faraday pattern presents quite different behaviours (such as the excitations and the motions) when the system crosses from the BEC side to the BCS side. The coupling not only plays an important role in the parametric excitation, but also determines the dominant wavelength of the spatial structure. Along the crossover, the coupling effects are more significant in the BCS side. The final numerical investigation verifies these results and gives a detailed study of the parametric excitations (i.e. Faraday instability) and the 3D pattern formation.

Waves in a bounded two component electron-dust plasma

Taking into account the boundary, the dust charge variation, the dust size and particle density effects, waves in a two component electron-dust plasma, bounded by a cylindrical domain, are presented. The dispersion relation for the waves is obtained and investigated analytically. Some limiting cases are also discussed. It is shown that the mentioned effects have a strong influence on the dispersion properties of the waves. The finite geometry not only modifies the frequencies of the excited modes, but it also has significant influence on the damping rate of the long waves.

Phase diagram of disordered two-dimensional extended Bose-Hubbard model

By using the inhomogeneous mean-field theory, the phase diagram of the two-dimensional soft-core extended Bose-Hubbard model with both on-site and nearest-neighbor interactions in the presence of spatial disorder is determined. Rich phases, including Mott-insulator, checkerboard solid, supersolid, superfluid and disordered solid are obtained. Interestingly, due to the presence of disorder, a new disordered solid phase is found between the incompressible lobes, and it is demonstrated that the supersolid phase can survive in two-dimensional soft-core bosons. Furthermore, the system undergoes the phase transition from a disordered solid into a solid order or supersolid landscape when the disorder strength is increased. For weak nearest-neighbor repulsion, the increase of the disorder strength induces both checkerboard solid and supersolid phases shrinking to smaller hopping regions. However, for strong nearest-neighbor repulsion, the disorder stabilizes the supersolid phase and makes it occupying a remarkably broad region in the phase diagram. The analytical expressions for the phase boundaries between the incompressible and compressible phases are also obtained, which are in qualitative agreement with our numerical results.

Direct laser acceleration in an inhomogeneous cylindrical plasma channel

We discuss the development of the instability for electron acceleration and energy gain of electrons from laser waves in both homogeneous and inhomogeneous non-planar cylindrical plasma channels. We find that the instability (i.e., electron acceleration) in the cylindrical plasma channel can be developed more quickly and strongly than that in the planar two-dimensional plasma channel. Then, enhancement of energy gain and shortening of acceleration length in the cylindrical plasma channel are observed. For the cylindrical plasma channel, the electron in the inhomogeneous plasma channel can gain more energy from the laser and the acceleration length can be shortened by adjusting the width of the laser and the inhomogeneous charge density distributions.

The characteristics of an intense laser beam propagating in a corrugated plasma channel

The propagation of an intense laser beam in a corrugated plasma channel is investigated. By using the source-dependent expansion technique, an evolution equation of the laser spot size is derived. The behaviors including aperiodic oscillation, resonance, beat-like wave, and periodic oscillation with multipeak are found and analyzed. The formula for the instantaneous wave numbers of these oscillations is obtained. These theoretical findings are confirmed by the final numerical simulation.

Quantum Phase Transition and Local Entanglement in Extended Hubbard Model on Anisotropic Triangular Lattices

Using a mean-field theory based upon Hartree—Fock approximation, we theoretically investigate the competition between the metallic conductivity, spin order and charge order phases in a two-dimensional half-filled extended Hubbard model on anisotropic triangular lattice. Bond order, double occupancy, spin and charge structure factor are calculated, and the phase diagram of the extended Hubbard model is presented. It is found that the interplay of strong interaction and geometric frustration leads to exotic phases, the charge fluctuation is enhanced and three kinds of charge orders appear with the introduction of the nearest-neighbor interaction. Moreover, for different frustrations, it is also found that the antiferromagnetic insulating phase and nonmagnetic insulating phase are rapidly suppressed, and eventually disappeared as the ratio between the nearest-neighbor interaction and on-site interaction increases. This indicates that spin order is also sensitive to the nearest-neighbor interaction. Finally, the single-site entanglement is calculated and it is found that a clear discontinuous of the single-site entanglement appears at the critical points of the phase transition.