Microscopic Model for Sequential Tunneling in Semiconductor Multiple Quantum Wells

We propose a selfconsistent microscopic model of vertical sequential tunneling through a multi-quantum well.The model includes a detailed description of the contacts,uses the Transfer Hamiltonian for expressions of the current and it treats the Coulomb interaction within a mean field approximation. We analyze the current density through a double well and a superlattice and study the formation of electric field domains and multistability coming from the Coulomb interaction. Phase diagrams of parameter regions (bias, doping in the heterostructure and in the contacts,etc) where the different solutions exist are given.Comment: 4 pages, 8 Postscript Figure

Non-equilibrium correlations and entanglement in a semiconductor hybrid circuit-QED system

We present a theoretical study of a hybrid circuit-QED system composed of two semiconducting charge-qubits confined in a microwave resonator. The qubits are defined in terms of the charge states of two spatially separated double quantum dots (DQDs) which are coupled to the same photon mode in the microwave resonator. We analyze a transport setup where each DQD is attached to electronic reservoirs and biased out-of-equilibrium by a large voltage, and study how electron transport across each DQD is modified by the coupling to the common resonator. In particular, we show that the inelastic current through each DQD reflects an indirect qubit-qubit interaction mediated by off-resonant photons in the microwave resonator. As a result of this interaction, both charge qubits stay entangled in the steady (dissipative) state. Finite shot noise cross-correlations between currents across distant DQDs are another manifestation of this nontrivial steady-state entanglement.Comment: Final versio

Current self-oscillations, spikes and crossover between charge monopole and dipole waves in semiconductor superlattices

Self-sustained current oscillations in weakly-coupled superlattices are studied by means of a self-consistent microscopic model of sequential tunneling including boundary conditions naturally. Well-to-well hopping and recycling of charge monopole domain walls produce current spikes (high frequency modulation) superimposed on the oscillation. For highly doped injecting contacts, the self-oscillations are due to dynamics of monopoles. As the contact doping decreases, a lower-frequency oscillatory mode due to recycling and motion of charge dipoles is predicted. For low contact doping, this mode dominates and monopole oscillations disappear. At intermediate doping, both oscillation modes coexist as stable solutions and hysteresis between them is possible.Comment: 4 pages, 4 figure

Majorana Zero Modes in Graphene

A clear demonstration of topological superconductivity (TS) and Majorana zero modes remains one of the major pending goal in the field of topological materials. One common strategy to generate TS is through the coupling of an s-wave superconductor to a helical half-metallic system. Numerous proposals for the latter have been put forward in the literature, most of them based on semiconductors or topological insulators with strong spin-orbit coupling. Here we demonstrate an alternative approach for the creation of TS in graphene/superconductor junctions without the need of spin-orbit coupling. Our prediction stems from the helicity of graphene's zero Landau level edge states in the presence of interactions, and on the possibility, experimentally demonstrated, to tune their magnetic properties with in-plane magnetic fields. We show how canted antiferromagnetic ordering in the graphene bulk close to neutrality induces TS along the junction, and gives rise to isolated, topologically protected Majorana bound states at either end. We also discuss possible strategies to detect their presence in graphene Josephson junctions through Fraunhofer pattern anomalies and Andreev spectroscopy. The latter in particular exhibits strong unambiguous signatures of the presence of the Majorana states in the form of universal zero bias anomalies. Remarkable progress has recently been reported in the fabrication of the proposed type of junctions, which offers a promising outlook for Majorana physics in graphene systems.Comment: 14 pages, 8 figures. Included simulations of Andreev spectroscopy and mor

Dielectric Function of Diluted Magnetic Semiconductors in the Infrared Regime

We present a study of the dielectric function of metallic (III,Mn)V diluted magnetic semiconductors in the infrared regime. Our theoretical approach is based on the kinetic exchange model for carrier induced (III,Mn)V ferromagnetism. The dielectric function is calculated within the random phase approximation and, within this metallic regime, we treat disorder effects perturbatively and thermal effects within the mean field approximation. We also discuss the implications of this calculations on carrier concentration measurements from the optical f-sum rule and the analysis of plasmon-phonon coupled modes in Raman spectra.Comment: 6 pages, 6 figures include

Quantum versus classical counting in nonMarkovian master equations

We discuss the description of full counting statistics in quantum transport with a nonMarkovian master equation. We focus on differences arising from whether charge is considered as a classical or a quantum degree of freedom. These differences manifest themselves in the inhomogeneous term of the master equation which describes initial correlations. We describe the influence on current and in particular, the finite-frequency shotnoise. We illustrate these ideas by studying transport through a quantum dot and give results that include both sequential and cotunneling processes. Importantly, the noise spectra derived from the classical description are essentially frequency-independent and all quantum noise effects are absent. These effects are fully recovered when charge is considered as a quantum degree of freedom.Comment: 12 pages; 3 figure

Actualización en malformaciones venosas

Venous malformations represent 2/3rds of all vascular malformations and are frequently much more complex than they appear to be. Patients with large venous malformations require a deep analytical and radiological study, as well as specific treatment to control any possible localised intravascular coagulation. If the lesions are extensive, especially in the lower member, a study should be made to detect the presence of an underlying osteoporosis with the idea of preventing pathological fractures. Equally, a check must be made for arthropathy, and an early prophylactic synovectomy must be considered when the radiological extension makes this advisable, with the idea of avoiding irreversible damage to the joints with the passage of time. Currently, microfoam scleropathy is favoured as the treatment of choice for low-flow vascular malformations. In the not too distant future, the use of selective antiangiogenic medicines, besides low-molecularweight heparins

The Two-impurity Anderson Model Revisited: Competition between Kondo Effect and Reservoir-mediated Superexchange in Double Quantum Dots

We study a series-coupled double quantum dot in the Kondo regime modeled by the two-impurity Anderson model and find a new conduction-band mediated superexchange interaction that competes with Kondo physics in the strong Coulomb interaction limit. Our numerical renormalization group results, complemented with the higher-order Rayleigh-Schr\"odinger perturbation theory, show that the novel exchange mechanism leads to clear experimental consequences that can be checked in transport measurements through double quantum dots

Factores prenatales asociados al incumplimiento del esquema básico de vacunación en menores de 5 años: Prenatal factors associated with breach of the basic vaccination scheme in under 5 years of age

Objective: To determine the prenatal risk factors associated with the failure to comply with the basic vaccination scheme in children under 5 years of age, based on the Demographic and Family Health Survey (ENDES) of 2018. Materials and Methods: It is an observational, retrospective, analytical and transversal study. We study the sample of the National Demographic and Health Survey (ENDES) for 2018 that includes 18 104 children between 1 and 5 years with health card seen in the interview, finding the results in the INEI surveys. The files containing the vaccination scheme questionnaires are selected and the data processed with SPSS version 25. The statistical processing is analytical and descriptive, bivariate and multivariate with the help of STATA v16 and Excel 2016. Results: There was a final sample of 18,104 children between 1 to 5 years old in 2018. The multivariate analysis found the association of non-compliance with the vaccination schedule with the mother's age (p value = <0.01, PR = 1.20, CI = 1.13 - 1.28), the number of controls inadequate (p value = <0.01, PR = 1.28, CI = 1.23 - 1.33) and the pregnant woman did not receive the tetanus vaccine during pregnancy (p= <0.01, RP= 1.16, CI= 1.12 - 1.20). No such association was found with the place of residence, wealth index and natural region. Conclusions: The prenatal risk factors associated with the failure to comply with the basic vaccination scheme in children under 5 years of age were maternal age, the number of inadequate prenatal check-ups and the pregnant woman who had not received the tetanus vaccine.Objetivo: Determinar los factores de riesgo prenatales asociados al incumplimiento del esquema básico de vacunación en menores de 5 años a partir de la encuesta demográfica y de salud familiar (ENDES) del año 2018. Materiales y Métodos: Es un estudio observacional, retrospectivo, analítico y transversal. Se estudia la muestra de la Encuesta Nacional Demográfica y de Salud (ENDES) del año 2018 que comprende a 18 104 niños entre 1 a 5 años con tarjeta de salud vista en la entrevista, encontrándose los resultados en las encuestas del INEI. Se selecciona los archivos que contienen los cuestionarios del esquema de vacunación y se procesan los datos con SPSS versión 25. El procesamiento estadístico es de tipo analítico y descriptivo, bivariado y multivariado con ayuda de STATA v16 y Excel 2016. Resultados: Se contó con una muestra final de 18 104 de menores entre 1 a 5 años el 2018. En el análisis multivariado se encontró la asociación del incumplimiento de esquema de vacunación con la edad de la madre (valor p= <0,01, RP= 1,20, IC= 1,13 – 1,28), el número de controles no adecuados (valor p= <0,01, RP= 1,28, IC= 1,23 – 1,33) y la gestante no haber recibido la vacuna antitetánica en el embarazo (valor p= <0,01, RP= 1,16, IC= 1,12 – 1,20). No se encontró dicha asociación con el lugar de residencia, índice de riqueza y región natural. Conclusiones: Los factores de riesgo prenatales asociados al incumplimiento del esquema básico de vacunación en menores de 5 años fueron la edad materna, el número de controles prenatales inadecuados y la gestante no haber recibido la vacuna antitetánica

Au-Cu/SBA(Ti) based catalysts for photocatalytic applications

Comunicación a congresoIn this work, it has been synthesized several Au and Au-Cu alloy photocatalysts supported on two different mesoporous supports: a non-commercial SBA-15 and a post-synthesis TiO2 modified SBA-15 (TiSBA-15), with which a high dispersion of TiO2 species have been achieved maintaining the SBA-15 structure. In addition, it has also been obtained highly dispersed Au nanoparticles confined in SBA-15 pore channels, as can be observed in Figure 1. The photocatalysts have been preliminary tested in the preferential CO oxidation in a H2-rich stream (CO-PROX) at room temperature and atmospheric pressure under simulated solar light irradiation. In spite of the very low gold and copper loading (1.5 wt% and 0.5wt% respectively), the catalysts resulted active and selective in the low temperature photo-CO-PROX.Universidad de Málaga, Campus de Excelencia Internacional Andalucía Tec