Finite-size Effects in a Two-Dimensional Electron Gas with Rashba Spin-Orbit Interaction

Within the Kubo formalism, we estimate the spin-Hall conductivity in a two-dimensional electron gas with Rashba spin-orbit interaction and study its variation as a function of disorder strength and system size. The numerical algorithm employed in the calculation is based on the direct numerical integration of the time-dependent Schrodinger equation in a spin-dependent variant of the particle source method. We find that the spin-precession length, L_s controlled by the strength of the Rashba coupling, establishes the critical lengthscale that marks the significant reduction of the spin-Hall conductivity in bulk systems. In contrast, the electron mean free path, inversely proportional to the strength of disorder, appears to have only a minor effect.Comment: 5 pages, 3 figure

Spin-Hall Effect in A Symmetric Quantum Wells by A Random Rashba Field

Changes dopant ion concentrations in the sides of a symmetric quantum well are known to create a random Rashba-type spin-orbit coupling. Here we demonstrate that, as a consequence, a finite size spin-Hall effect is also present. Our numerical algorithm estimates the result of the Kubo formula for the spin-Hall conductivity, by using a tight-binding approximation of the Hamiltonian in the framework of a time-dependent Green's function formalism, well suited for very large systems.Comment: 4 pages, 4 figures in eps forma

Thermodynamic Limits of the Local Field Corrections in a Spin-Polarized Electron System

In a spin-polarized electron gas, the effect of the exchange ͑x͒ and correlation ͑c͒ interactions can be incorporated into the dynamic response functions through spin-dependent local-field corrections G␴ x,c(␻,qជ). We obtain the zero-frequency and long-wavelength limits of G␴ x,c(␻,qជ) by analyzing the connection between the macroscopic response function and the thermodynamic parameters of the system

Magnetoacoustic Plasmons in a Bilayer Quasi-Two-Dimensional Spin-Polarized System

We investigate the charge and spin response functions of a bilayer quasi-two-dimensional system, spin polarized by a constant magnetic field B ជ . Terms beyond the random-phase approximation, the exchange and correlation interactions, are introduced by using generalized spin-dependent local field factors, G␴ x,c(qជ,␻). The self-consistent magnetic interaction among the electron spins determines the coupling of the charge and the longitudinal spin-density excitations, leading to coupled in-phase and out-of-phase electric and magnetic modes. We find that the lowest frequency belongs to an acoustic mode, that represents the out-of-phase oscillation of the longitudinal magnetizations in the two layers. This collective excitation is shown to become important in the case of materials with large gyromagnetic factors, such as dilute magnetic semiconductors

Retarded long-range potentials for the alkali-metal atoms and a perfectly conducting wall

The retarded long-range potentials for hydrogen and alkali-metal atoms in their ground states and a perfectly conducting wall are calculated. The potentials are given over a wide range of atom-wall distances and the validity of the approximations used is established.Comment: RevTeX, epsf, 11 pages, 2 fig

Zeros of Rydberg-Rydberg Foster Interactions

Rydberg states of atoms are of great current interest for quantum manipulation of mesoscopic samples of atoms. Long-range Rydberg-Rydberg interactions can inhibit multiple excitations of atoms under the appropriate conditions. These interactions are strongest when resonant collisional processes give rise to long-range C_3/R^3 interactions. We show in this paper that even under resonant conditions C_3 often vanishes so that care is required to realize full dipole blockade in micron-sized atom samples.Comment: 10 pages, 4 figures, submitted to J. Phys.

Examining the right-wing extremism in the EU: a comparison between the origins and development o far-right extremism in Ireland, Spain, and Romania

The right-wing extremismhas been having a significant presencein the European Union in the last couple of years. This study aims to analyse the origins and development of the right-wing extremism in the European Union after the World War II, while examining the cases of Ireland, Spain and Romania. This analysis isfocused on countries with different historical backgrounds,social contexts and amplitudes of right-wing extremist activity. Considering the heterogeneity of the right-wing extremism and its manifestations, it is expected a diversity of criteria of exclusion (such as nationalism, xenophobia, racism, etc.), shaped within the national context.L'extremisme de dretes ha tingut una presència important a la Unió Europea en els darrers dos anys. Aquest estudi té com a objectiu analitzar els orígens i el desenvolupament de l'extremisme de dretes a la Unió Europea després de la Segona Guerra Mundial, tot examinant els casos d'Irlanda, Espanya i Romania. Aquesta anàlisi se centra en països amb diferents antecedents històrics, contextos socials i amplituds d'activitat extremista de dretes. Tenint en compte l'heterogeneïtat de l'extremisme de dretes i les seves manifestacions, s'espera una diversitat de criteris d'exclusió (com el nacionalisme, la xenofòbia, el racisme, etc.), configurats dins del context nacional

Macrodimers: ultralong range Rydberg molecules

We study long range interactions between two Rydberg atoms and predict the existence of ultralong range Rydberg dimers with equilibrium distances of many thousand Bohr radii. We calculate the dispersion coefficients $C_{5}$, $C_{6}$ and $C_{8}$ for two rubidium atoms in the same excited level $np$, and find that they scale like $n^{8}$, $n^{11}$ and $n^{15}$, respectively. We show that for certain molecular symmetries, these coefficients lead to long range potential wells that can support molecular bound levels. Such macrodimers would be very sensitive to their environment, and could probe weak interactions. We suggest experiments to detect these macrodimers.Comment: 4 pages, submitted to PR