Aharonov-Bohm oscillations and electron gas transitions in hexagonal core-shell nanowires with an axial magnetic field

We use spin-density-functional theory within an envelope function approach to calculate electronic states in a GaAs/InAs core-shell nanowire pierced by an axial magnetic field. Our fully 3D quantum modeling includes explicitly the description of the realistic cross-section and composition of the sample, and the electrostatic field induced by external gates in two different device geometries, gate-all-around and back-gate. At low magnetic fields, we investigate Aharonov-Bohm oscillations and signatures therein of the discrete symmetry of the electronic system, and we critically analyze recent magnetoconductance observations. At high magnetic fields we find that several charge and spin transitions occur. We discuss the origin of these transitions in terms of different localization and Coulomb regimes and predict their signatures in magnetoconductance experiments

SLAM-based 3D outdoor reconstructions from lidar data

The use of depth (RGBD) cameras to reconstruct large outdoor environments is not feasible due to lighting conditions and low depth range. LIDAR sensors can be used instead. Most state of the art SLAM methods are devoted to indoor environments and depth (RGBD) cameras. We have adapted two SLAM systems to work with LIDAR data. We have compared the systems for LIDAR and RGBD data by performing quantitative evaluations. Results show that the best method for LIDAR data is RTAB-Map with a clear difference. Additionally, RTAB-Map has been used to create 3D reconstructions with and without photometry from a visible color camera. This proves the potential of LIDAR sensors for the reconstruction of outdoor environments for immersion or audiovisual production applicationsPeer ReviewedPostprint (author's final draft

Emission spectrum of quasi-resonant laterally coupled quantum dots

We calculate the emission spectrum of neutral and charged excitons in a pair of laterally coupled InGaAs quantum dots with nearly degenerate energy levels. As the interdot distance decreases, a number of changes take place in the emission spectrum which can be used as indications of molecular coupling. These signatures ensue from the stronger tunnel-coupling of trions as compared to that of neutral excitons.Comment: 7 pages, 7 figure

Geometric model and calibration method for a solid-state LiDAR

This paper presents a novel calibration method for solid-state LiDAR devices based on a geometrical description of their scanning system, which has variable angular resolution. Determining this distortion across the entire Field-of-View of the system yields accurate and precise measurements which enable it to be combined with other sensors. On the one hand, the geometrical model is formulated using the well-known Snell’s law and the intrinsic optical assembly of the system, whereas on the other hand the proposed method describes the scanned scenario with an intuitive camera-like approach relating pixel locations with scanning directions. Simulations and experimental results show that the model fits with real devices and the calibration procedure accurately maps their variant resolution so undistorted representations of the observed scenario can be provided. Thus, the calibration method proposed during this work is applicable and valid for existing scanning systems improving their precision and accuracy in an order of magnitude.Peer ReviewedPostprint (published version

Panteons Reials de Poblet 2.0

El desenvolupament web ha canviat molt els darrers anys, i la forma de presentar el contingut ha evolucionat. Aquí situem aquest projecte. La pàgina web actual dels Panteons Reials de Poblet ha quedat obsoleta i l’objectiu principal és mostrar i gestionar el contingut de forma més fàcil i dinàmica. Per assolir aquest objectiu, serà necessari utilitzar el conegut gestor de contingut Wordpress i una extensió pròpia per tal de mostrar els arbres genealògics dels llinatges més importants del monestir de Poblet. L’èxit del projecte dependrà de dos factors: el primer, que les necessitats del projecte quedin ben definides; segon, que l’acoblament de Wordpress i l’extensió funcioni perfectament.Website development has changed in recent years, and so has done, how contents are presented. Is in this context where this projects is placed. Royal mausoleums of Poblet’s current website had become obsolete, so the main objective has been to make it easier to manage and to show the contents. In order to fulfill this goal, it has been used the well-known content manager Wordpress and an own extension to show family trees of the most important lineages of the monastery of Poblet. The project success will depend on the good definition of the project needs, and the good cohesion between Wordpress and the extension

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

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

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

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