From quantum dots to quantum wires: electronic structure of semiconductor nanorods

The transition bridge between zero-dimensional quantum dots and one-dimensional quantum wires is explored theoretically by means of the construction of the addition energy spectra of nanorods with different lengths. Spin density-functional theory supplemented with full configuration interaction calculations are carried out. The addition energy spectra are qualitatively related to the single particle correlation diagram. The transition from charge-density waves to spin-density waves, characterizing the Wigner crystallization in the low density limit is show

Programa de Intervención en Población Inmigrante Africana con VIH/SIDA: PIPIAVS

Desde los años 80, la propagación del VIH se ha convertido en una de las mayores crisis de salud pública en todo el mundo. Colectivos como el de inmigrantes africanos han mostrado una gran vulnerabilidad en España, convirtiéndolos en uno de los grupos con más porcentaje de infectados por VIH. Por ello, el programa de intervención que se presenta tiene como objetivo principal conseguir una mejora del bienestar psicológico en 30 inmigrantes africanos de ambos sexos y con edad a partir de los 18 años, que actualmente estén en tratamiento antirretroviral ante el VIH. Todos los participantes responderán a una batería de cuestionarios previamente y posteriormente a realizar la intervención con el objetivo de evaluar la eficacia de éste. El programa va a consistir en 10 sesiones de alrededor de 60 minutos cada una, y programadas durante 5 semanas. Se trabajarán contenidos informativos relacionados con el VIH y la inmigración, se trabajarán habilidades sociales, manejo del estrés y gestión emocional. Tras la aplicación del programa se puede esperar que los participantes mejoren en las variables trabajadas. Así, el objetivo del programa se habrá cumplido, que era mejorar el bienestar psicológico de los participantes.<br /

Strong configuration mixing due to dielectric confinement in semiconductor nanorods

The interaction between electron-electron and electron-hole pairs in semiconductor nanorods embedded in dielectric media is investigated using a configuration-interaction method. Contrary to spherical quantum dots of similar volume, the dielectric confinement is shown to bring nanorods into a regime of strong configuration mixing. The wave functions are particularly sensitive to such mixing, which leads to qualitative changes in the electronic and optical properties of the rod

Correlation in narrow nanorods: a variational potential–configuration interaction scheme

Abstract. Full configuration interaction calculations of two electrons in narrow semiconductor nanorods are carried out employing different orbital basis sets. It is shown that the usual configurations built from single-particle states cannot yield a correct singlet-triplet energetic order regardless of the basis size, as they miss correlation energy. Mean-field optimized orbitals partially correct this drawback. A new approach is introduced, based on a simple variational procedure, which yields robust result

Isospin phases of vertically coupled double quantum rings under the influence

Vertically coupled double quantum rings submitted to a perpendicular magnetic field B are addressed within the local spin-density-functional theory. We describe the structure of quantum ring molecules containing up to 40 electrons considering different inter-ring distances and intensities of the applied magnetic field. When the rings are quantum mechanically strongly coupled, only bonding states are occupied and the addition spectrum of the artificial molecules resembles that of a single-quantum ring, with some small differences appearing as an effect of the magnetic field. Despite the latter’s tendency to flatten the spectra, in the strong-coupling limit, some clear peaks are still found even when B 0 that can be interpretated from the single-particle energy levels similarly as in the zero magnetic field case, namely, in terms of closed-shell and Hund’s-rule configurations. By increasing the inter-ring distance, the occupation of the first antibonding orbitals washes out such structures and the addition spectra become flatter and irregular. In the weak-coupling regime, numerous isospin oscillations are found as functions of

Diamagnetic and paramagnetic shifts in self-assembled InAs lateral quantum dot molecules

We uncover the underlying physics that explains the energy shifts of discrete states of individual InAs lateral quantum dot molecules (LQDMs) as a function of magnetic fields applied in the Faraday geometry. We observe that ground states of the LQDM exhibit a diamagnetic shift while excited states exhibit a paramagnetic shift. We explain the physical origin of the transition between these two behaviors by analyzing the molecular exciton states with effective mass calculations. We find that charge carriers in delocalized molecular states can become localized in single QDs with increasing magnetic field. We further show that the net effects of broken symmetry of the molecule and Coulomb correlation lead to the paramagnetic response.NSF DMR-0844747 DMR 1309989 GV VALi+d Grant APOSTD/2013/052 NRF of Korea 2011-C0030821/2013R1A1A1007118 MINECO Project CTQ2011-2732