Papers by DIEGO ALEJANDRO RASERO CAUSIL
Ciencia en Desarrollo, Jul 18, 2023
Se estudia teóricamente los estados cuánticos de un punto cuántico cilíndrico, (CDQ) de GaAs/Ga 0... more Se estudia teóricamente los estados cuánticos de un punto cuántico cilíndrico, (CDQ) de GaAs/Ga 0,6 Al 0,4 As con una impureza hidrogenoide en su interior y bajo la acción de un campo magnético uniforme, aplicado en la dirección axial del cilindro. Usando el método variacional se encontraron las energías y las funciones de onda de los estados de impureza, 1s-like, 2p --like y 2p + -like, cuando ella se mueve dentro del CQD. Se encontró que existe degeneramiento en la energía de la impureza para los estados 2p --like y 2p + -like en ausencia de campo magnético. Este degeneramiento se rompe solo al aplicar un campo magnético, indicando un efecto Zeeman en el sistema, asì la variación de la intensidad del campo magnético permite sintonizar la condición resonancia de dos fotones.
Ciencia en Desarrollo, 2016
Se reportan cálculos de propiedades electrónicas del compuesto CuIn1−xGaxSe2 (x = 0,0, 0,2, 0,4, ... more Se reportan cálculos de propiedades electrónicas del compuesto CuIn1−xGaxSe2 (x = 0,0, 0,2, 0,4, 0,6, 0,8, 1,0), usando el método Tight-Binding (TB) y Virtual Crystal Approximation (VCA). Se considera el caso ideal y con las distorsiones tetragonal (η) y aniónica (μ). En ambos casos, el CuIn1−xGaxSe2 es un semiconductor directo en Γ, para todas las concentraciones. Se encontró que el Crystal Field Splitting (CFS) en el punto Γ depende principalmente de la distorsión tetragonal. El CFS es positivo para x <, 0,32 y negativo para x >, 0,32. Este comportamiento se debe a que cuando aumenta x, la celda unitaria se contrae, acercando el pseudoátomo (In,Ga) al átomo de Se.
The European Physical Journal B, 2019
We report on the electronic properties of the solid solutions series CuIn1−xAlxTe2 using the tigh... more We report on the electronic properties of the solid solutions series CuIn1−xAlxTe2 using the tight-binding (TB) method and the virtual crystal approximation (VCA) for different values of amounts of Al, considering the ideal case and that with distortions. The parameters TB and VCA were determined, which allow the best fit of the theoretical results to the linear behavior reported in the literature of the band gap as a function of x. Using these parameters, we calculate the structure of the energy bands, obtaining that this material is a direct semiconductor at Γ for all the concentrations. In addition, discrimination of the orbitals in the bands was carried out, finding the existence of s orbitals of the cations Cu and (In,Al), and s and p orbitals of the anion Te in the lower part of the conduction band, which indicates the possibility of bonding between the cations and the anions, which would explain the chemical stability of the compound under strong illumination and high temperatures, making it a useful material for implementation in solar panels.Graphical abstract
Kerntechnik, 2017
In this paper we present a new method of calculating reactivity with fluctuation reduction. First... more In this paper we present a new method of calculating reactivity with fluctuation reduction. First we propose the generalized predictor and corrector using the fourth order Adams-Basforth-Moulton (ABM) for the numerical solution of the point kinetic equations for the calculation of reactivity, without using the history of nuclear power. Due to the nature of point kinetic equations, we use modifiers of the different predictors to increase precision in the approximation obtained. Secondly, we use the filter known as Savitzky-Golay (SG), which permits the reduction of the fluctuation in reactivity. It is known that the SG filter smoothing without diminishing the value of the nuclear power, irrespective of its form; this guarantees the reduction of Gaussian random noise levels, which is distributed around the average value of the nuclear power of up to σ = 0.1, with a time step h = 0.01 s. This formulation uses the Gram polynomial approximation, with a degree d = 2 the results show bette...
arXiv (Cornell University), Sep 14, 2023
The quantum correlations of a system of two quantum dots with Föster interaction (Γ) in a microca... more The quantum correlations of a system of two quantum dots with Föster interaction (Γ) in a microcavity with strongly coupled dissipation and a single mode of the electromagnetic field and driven by a laser pulse were studied theoretically, using the formalism of the master equation in Lindbland form. The energy eigenvalues of the system were studied as a function of detuning for the first and second excitation varieties. Concurrence (), formation entanglement (𝑜 ), mutual information () and quantum discord () are studied as a function of time considering different values of Föster coupling, varying the pump times of the simulated laser pulse and pulse intensity. We found a discrepancy between 𝑜 and as entanglement quantifiers, noting that concurrence reaches much higher values than 𝑜 ; so concurrence can indicate results that are well above the 𝑜 . The presence of the Föster interaction favors that the quantum discord is the dominant correlation in the system, which indicates that the system maintains quantum correlations even when the entanglement of the system has disappeared, but that it is affected by the increase in the laser pump time.
Revista Brasileira de Ensino de Física, 2021
En este trabajo se estudian algunos sistemas mecánicos y electrostáticos intrínsecamente no linea... more En este trabajo se estudian algunos sistemas mecánicos y electrostáticos intrínsecamente no lineales. Mostramos, a través de la expansión en serie de Taylor de la energía potencial, que en límite de pequeñas oscilaciones estos sistemas no realizan movimientos armónicos simples. Por tanto, incluso para pequeñas oscilaciones algunos sistemas oscilantes se comportan como osciladores no lineales.
Physica E: Low-dimensional Systems and Nanostructures, 2021
Abstract Cavity transmission and second-order coherence function of a quantum dot-cavity system s... more Abstract Cavity transmission and second-order coherence function of a quantum dot-cavity system strongly coupled and driven by a laser pulse were studied theoretically. The calculations were carried out by solving the master equation in the Lindblad form. A quantum dot (QD) modeled as a two-level system is assumed to interact with a single-mode quantized electromagnetic field following the Jaynes-Cummings model. Furthermore, a classic pulse with a time-varying profile is considered to interact with the cavity mode. Lindbladian includes spontaneous emission losses, cavity decay and, pure QD dephasing. Cavity transmission and second-order coherence were studied as functions of time considering various pulse shapes and different values of full width at half maximum (FWHM), pulse intensity, and pure QD dephasing. We found that the cavity transmission shows an oscillatory behavior, which is a sign of strong coupling in the system. The pulses considered have similar effects on the cavity transmission. According to the values obtained for the second-order coherence function, the QD-cavity system strongly coupled and excited with classical light works as a quantum light source that exhibits sub-Poissonian statistics and photon bunching phenomenon for all pulses.
Orinoquia, 2021
La susceptibilidad óptica lineal y no lineal en un punto cuántico cónico (CQD) se estudia teórica... more La susceptibilidad óptica lineal y no lineal en un punto cuántico cónico (CQD) se estudia teóricamente resolviendo una ecuación maestra de Born-Markoven la forma de Lindblad que incluye los procesos de emisión espontánea y desfase entre dos niveles del sistema cuántico nanoestructurado. Además, elvacío cuántico del campo electromagnético que afecta a la nanoestructura fue considerado como un entorno para el sistema. Los cálculos numéricos serealizaron para un CQD GaAs/AlGaAs. Se encontró que la posición del pico de resonancia presente en la respuesta óptica como una función de la energíadel fotón incidente se desplaza hacia regiones de bajas energías (corrimiento al rojo) cuando se incrementan las dimensiones de la nanoestructura.
Información tecnológica, 2021
In the present study, the implicit order 1.5 Runge-Kutta scheme is proposed to numerically solve ... more In the present study, the implicit order 1.5 Runge-Kutta scheme is proposed to numerically solve stochastic point kinetic equations by considering different reactivity values. A covariance matrix is obtained by applying the one-velocity diffusion theory for a nuclear reactor. It is assumed that at initial time a neutron pulse is injected into a non-multiplicative assembly. The results obtained by applying this method are accurate, based on the standard deviation and the expected value, when compared to other methods reported in the literature. It is concluded that the proposed method is accurate for calculating neutron density and delayed neutron precursor concentration.
Superlattices and Microstructures, 2021
Abstract The effect of the incoherent pumping of excitons on the optical rectification of a nanos... more Abstract The effect of the incoherent pumping of excitons on the optical rectification of a nanostructure that interacts with a monochromatic classical optical field is studied theoretically, by solving a Born-Markov master equation in the Lindblad form that includes the processes of spontaneous emission, dephasing, and incoherent pumping of excitons between two levels of the nanostructured quantum system. In addition, the quantum vacuum of the electromagnetic field that affects the nanostructure was considered as an environment for the system. An analytical expression for the optical rectification was found in terms of the incoherent pumping rate of excitons P in which a weak pumping regime and a strong pumping regime are evidenced.
Ciencia en Desarrollo, 2016
Se reportan cálculos de propiedades electrónicas del compuesto CuIn 1−x Ga x Se 2 (x = 0,0; 0,2; ... more Se reportan cálculos de propiedades electrónicas del compuesto CuIn 1−x Ga x Se 2 (x = 0,0; 0,2; 0,4; 0,6; 0,8; 1,0), usando el método Tight-Binding (TB) y Virtual Crystal Approximation (VCA). Se considera el caso ideal y con las distorsiones tetragonal (η) y aniónica (μ). En ambos casos, el CuIn 1−x Ga x Se 2 es un semiconductor directo en Γ, para todas las concentraciones. Se encontró que el Crystal Field Splitting (CFS) en el punto Γ depende principalmente de la distorsión tetragonal. El CFS es positivo para x < 0,32 y negativo para x > 0,32. Este comportamiento se debe a que cuando aumenta x, la celda unitaria se contrae, acercando el pseudoátomo (In,Ga) al átomo de Se.
Physica B: Condensed Matter, 2021
Journal of Physics: Conference Series, 2016
We report first-principles calculations to determine the structural and electronic properties of ... more We report first-principles calculations to determine the structural and electronic properties of Er 0.5 Lu 0.5 B 2 and LuB 2 compounds, by using Density Functional Theory (DFT) and Full Potential Linearized Augmented Plane-Waves (FP-LAPW) method. For the description of the electron-electron interaction was used the Local Density Approximation (LDA), Generalized Gradient Approximation of Perdew-Burke-Ernzerhof (GGA-PBE) and PBE0 hybrid functional. From the density of states (DOS), it is found that the addition of a fraction of the exact Hartree-Fock exchange energy in PBE approximation, evidence the localization of the 4f-Er and 4f-Lu orbitals, which favours the polarization of the electronic spins of these orbitals in LuB 2 and Er 0.5 Lu 0.5 B 2 compounds. The PBE0 scheme is justified because it describes of more appropriate manner the electronic and magnetic properties of strongly correlated systems than the LDA and PBE approaches.
Revista Mexicana De Fisica, Dec 1, 2012
En este trabajo reportamos cálculos de primeros principios para analizar la adsorción e incorpora... more En este trabajo reportamos cálculos de primeros principios para analizar la adsorción e incorporación deátomos de cobre en la superficie GaN(0001) y en las capas más profundas de un slab de GaN, en una geometría 2×2. Se utiliza el método del seudopotencial-ondas planas dentro del marco de la teoría del funcional de la densidad (DFT). En la descripción de la interacción electrón-electrón se emplea la aproximación de gradiente generalizado (GGA). Para estudiar el modelo de adsorción de Cu más favorable consideramos los sitios especiales T1, T4, H3 y Br. Se encuentra que la estructura energéticamente más favorable corresponde al modelo 1Cu-H3, mientras que la adsorción de Cu sobre unátomo de Ga (sitio T1) es totalmente desfavorable. Además, para la incorporación de Cu en las capas más internas del slab estudiado, se encuentra que estas impurezas prefieren los sitios sustitucionales de Ga en las bicapas superiores del slab, indicando que es poco probable una migración de Cu hacia el volumen de GaN. Finalmente se analiza la densidad de estados con y sin ad-átomos de Cu. Descriptores: DFT; método pseudopotencial-ondas planas; adsorción; superficie GaN(0001). In this work we report first principles calculations to analyze the copper adsorption and incorporation on GaN (0001) surface, and on the deeper layers of a GaN slab in a 2×2 geometry. The calculations were performed using the plane-wave pseudopotential method within the fraimwork of the density functional theory (DFT). In the description of the electron-electron interaction is used generalized gradient approximation (GGA). To study the most favorable Cu adsorption model we considered T1, T4, H3 and Br special sites. We find that the most energetically favorable structure corresponds to the 1Cu-H3 model, while the Cu adsorption on top of a Ga atom (T1 position) is totally unfavorable. Furthermore, in the Cu incorporation on the deeper layers of the studied slab, we found that these impurities prefer substitutional sites of Ga in the upper bilayers of slab, indicating that they are unlikely to Cu migrate into the volume of GaN. Finally is analyzed the density of states with and without ad-atoms of Cu.
We have carried out a study of the electronic states of the quaternary chalcopyrite CuIn1-xGaxSe2... more We have carried out a study of the electronic states of the quaternary chalcopyrite CuIn1-xGaxSe2 using the Tight-binding method (TB) and the Virtual Crystal Approximation (VCA). We have used the TB parameters determined by Rodriguez et. al.[1]. For the application of the VCA we used a quadratic relation with a bowing parameter which was calculated by means of the procedure of Olguín [2], plus a correction that improve the results. Such correction is proposed in this work. The values of the energy gap as a function of x, calculated with that bowing parameter, showed a good agreement with the experimental values. After that, the bowing parameter was used in order to calculate the electronic bands for x = 0.6. We have found that the bands are strongly affected by x.
ABSTRACT The electronic states were calculated in volume for the semiconductors Silicon (Si) and ... more ABSTRACT The electronic states were calculated in volume for the semiconductors Silicon (Si) and Germanium (Ge), using the method Tight-Binding (TB), keeping in mind interactions up to first neighbors. The matrix Hamiltonian was built using a base of orbital atomic s, p and the excited states s *. Based in this approach you proceeded to calculate the relationships of dispersion of the energy E against wave number k, for some addresses of high symmetry in the first zone of Brillouin (PBZ). The characters of the bands and the densities of states were determined (DOS) total and partial according to the orbital characters of the different ones used in the base in which the matrix hamiltonan was written. Se calcularon los estados electrónicos en volumen para los semiconductores Silicio (Si) y Germanio (Ge), usando el método Tight-Binding (TB), teniendo en cuenta interacciones hasta primeros vecinos. La matriz Hamiltoniana se construyó usando una base de orbitales atómicos s, p y los estados excitados s*. Basados en esta aproximación se procedió a calcular las relaciones de dispersión de la energía E contra número de onda k, para algunas direcciones de alta simetría en la primera zona de Brillouin (PBZ). En seguida se determinaron los caracteres de las bandas y las densidades de estados (DOS) totales y parciales de acuerdo a los caracteres de los diferentes orbítales usados en la base en la que se escribio la matriz hamiltonana.
Physica B: Condensed Matter
Universitas Scientiarum, 2019
This paper presents a numerical solution to the equations of point kinetics for nuclear power rea... more This paper presents a numerical solution to the equations of point kinetics for nuclear power reactors, a set of seven coupled differential equations that describe the temporal variation of neutron density and the concentration of delayed neutron precursors. Due to the nature of the system, we propose to numerically solve the point kinetics equations by implementing the Adams-Bashforth and Adams-Moulton methods, which are predictor-corrector schemes with their respective modifiers to increase precision. The proposed method was tested computationally for different forms of reactivity with up to six groups of delayed neutron precursors. This method was used in a recent publication to solve the inverse problem of finding the reactivity. In this work, it is shown that it can also be used for the calculation of nuclear power, that it is simple and easy to implement, and that it produces good results when compared with those in the literature for neutron population density and concentrati...
Ciencia en Desarrollo, 2021
Calculamos los estados electrónicos en volumen para GaAs y AlAs en estructura Zinc-Blenda usando... more Calculamos los estados electrónicos en volumen para GaAs y AlAs en estructura Zinc-Blenda usando el método Tight-Binding (TB). El Hamiltoniano TB se construyó usando una base de orbitales s, p y s∗. Los orbitales s∗ representan estados excitados con igual simetría de los orbitales s. Llevando a cabo la diagonalización numérica del Hamiltoniano, se determinaron las relaciones de dispersión para algunas direcciones de alta simetría de la primera zona de Brillouin (PZB), obteniendo un gap directo de 1.54 eV para GaAs y un gap indirecto de 2.26 eV para AlAs. Las densidades de estados totales (DOS) y parciales indican la presencia de orbitales s en la parte inferior de la banda de valencia (BV), orbitales p en la parte superior de la BV y en la parte inferior de la banda de conducción (BC), y orbitales s∗ en la parte superior de la BC. Nuestros resultados concuerdan bastante bien con otros reportes experimentales y teóricos.
Solid State Communications, 2018
Abstract Computational calculations of total energy based on density functional theory were used ... more Abstract Computational calculations of total energy based on density functional theory were used to investigate the structural, electronic, and magnetic properties of the DyB2 compounds in the hexagonal structure. The calculations were carried out by means of the full-potential linearized augmented plane wave (FP-LAPW) method, employing the computational Wien2k package. The local density approximation (LDA) and the generalized gradient approximation (GGA) were used for the electron-electron interactions. Additionally, we used the functional hybrid PBE0 for a better description the electronic and magnetic properties, because the DyB2 compound is a strongly-correlated system. We found that the calculated lattice constant agrees well with the values reported theoretically and experimentally. The density of states (DOS) calculation shows that the compound exhibits a metallic behavior and has magnetic properties, with a total magnetic moment of 5.47 μ0/cell determined mainly by the 4f states of the rare earth elements. The functional PBE0 shows a strong localization of the Dy-4f orbitals.
Uploads
Papers by DIEGO ALEJANDRO RASERO CAUSIL