Abstract: Pinning of magnetic-field-induced Wigner molecules (WMs) confined in parabolic two-dimensional quantum dots by a charged defect is studied by an exact diagonalization approach. We found a re-entrant pinning of the WMs as a function of the magnetic field, a magnetic-field-induced re-orientation of the WMs and a qualitatively different pinning behaviour in the presence of a positive and negative Coulomb impurity.

Abstract: The behavior of nanoparticles in a low-pressure silane discharge is studied with the use of a self-consistent one-dimensional fluid model. Nanoparticles of a given (prescribed) radius are formed in the discharge by the incorporation of a dust growth mechanism, i.e., by including a step in which large anions (typically Si12H−25), produced in successive chemical reactions of anions with silane molecules, are transformed into particles. Typically a few thousand anions are used for one nanoparticle. The resulting particle density and the charge on the particles are calculated with an iterative method. While the spatial distribution and the charge of the particles are influenced by the plasma, the presence of the nanoparticles will in turn influence the plasma properties. Several simulations with different particle radii are performed. The resulting density profile of the dust will greatly depend on the particle size, as it reacts to the shift of the balance of the different forces acting on the particles.

Abstract: Strong terahertz (1THz=1012Hz) radiation can be generated by the electron oscillation in fs-laser-induced wake fields. The interaction of a fs-laser pulse with a low-density plasma layer is studied in detail using numerical simulations. The spatial distribution and temporal evolution of terahertz electron current developed in a low-density plasma layer are presented, which enables us to calculate the intensity distribution of THz radiation. It is shown that laser and plasma parameters, such as laser intensity, pulse width, and background plasma density, are of key importance to the process. The optimum condition for wake-field excitation and terahertz emission is discussed upon the simulation results. Radiation peaked at 6.4 THz, with 900 fs duration and 9% bandwidth, can be generated in a plasma of density 5×1017cm−3. It turns out that the maximum radiation intensity scales as n03a04 when wake field is resonantly excited, where n0 and a0 are, respectively, the plasma density and the normalized field amplitude of the laser pulse.