Pedro L. Contreras E.

University of the Andes (Venezuela) | ULA · Department of Physics

We perform a numerical study of the unitary regime as a function of disorder concentration in the imaginary part of the elastic scattering cross-section for the compound Sr2RuO4 in the flat band non-disperse limit. By using a self-consistent tight binding (TB) method, we find a couple of families of Wigner probabilistic functions that help to expla...

The exciting developments in the study of 2D monolayers have inspired us to explore the structural, magnetic , electronic and thermal properties of novel two-dimensional monolayers of transition metal oxy-halides NiXO (X = Cl, Br) by density functional theory calculations. The structural stability and thermo-dynamic stability of NiXO (X = Cl, Br) m...

Multi-azimuth walkaway vertical seismic profiling is an established technique for the estimation of in situ slowness surfaces and inferring anisotropy parameters. Normally, this technique requires the assumption of lateral homogeneity, which makes the horizontal slowness components at depths of downhole receivers equal to those measured at the surf...

The collision frequency (also known as the inverse scattering lifetime) can be self-consistently calculated from the imaginary part of the zero temperature elastic scattering cross-section in unconventional superconductors. We find these type of studies helpful to describe a hidden self-consistent damping due to incoherent fermions in two physical...

This work is aimed at numerically investigating the behavior of the Fermi energy in Strontium-doped Lanthanum Cuprate, using a numerical zero temperature elastic scattering cross-section procedure in the unitary collision regime. The main task is to vary the zero temperature superconducting energy gap from its zero value in the normal state, to the...

The collision frequency (also known as the inverse scattering lifetime) can be self-consistently calculated from the imaginary part of the zero temperature elastic scattering cross-section in unconventional superconductors. We find these type of studies helpful to describe a hidden self-consistent damping due to incoherent fermions in two physical...

This specialization aim to understand how the microscopic properties of atoms and molecules relate to classical thermodynamic properties and to some non-equilibrium phenomena. Teaches how to analyze and estimate the way thermodynamic materials behave and obtain appropriate equilibrium and non-equilibrium properties. Applies some computational ski...

The present work represents a review for the numerical calculation of the density of states (DoS) for two-dimensional tight-binding models with first neighbors in its normal state and for two superconducting order parameters. One is a singlet scalar state and the other is a triplet vector state. At the beginning an emphasis is given to the general...

This work is aimed at numerically investigating the behavior of the Fermi energy in Strontium-doped Lanthanum Cuprate, using a numerical zero temperature elastic scattering cross-section procedure in the unitary collision regime. The main task is to vary the zero temperature superconducting energy gap from its zero value in the normal state, to the...

Through this experience, I have learned how to engage students & boost learning in math and science with free virtual labs & sims from the University of Colorado at Boulder PhET Interactive Simulations project (https://phet.colorado.edu/en) In this specialization, we explored active learning strategies that teachers, instructors and lecturers can...

In this work, we present a review for the numerical calculation of the density of states (DOS) for two-dimensional tight-binding models with first neighbors in its normal state and for two superconducting order parameters. One is a singlet scalar state and the other is a triplet vector state. At the beginning an emphasis is given to the general exp...

The idea of applying the scattering lifetime calculated from the imaginary part of the zero temperature elastic scattering cross-section to study a hidden self-consistent damping in two spaces of importance for non-equilibrium statistical mechanics is proposed. It is discussed its relation with the classical phase space from statistical mechanics a...

The idea of applying the scattering lifetime calculated from the imaginary part of the zero temperature elastic scattering cross-section to study a hidden self-consistent damping in two spaces of importance for non-equilibrium statistical mechanics is proposed. It is discussed its relation with the classical phase space from statistical mechanics a...

With the advancement of two-dimensional monolayer, intensive study has been done on one- dimensional and zero-dimensional nanomaterials such as nanoribbons, nanowires and nanoflakes, nan- otubes etc. Here we have systematically explored the size, shape and spin resolved optical properties of two types of triangular nanoflakes (T1 and T2) of CrmSen...

Reviewer Certificate - Geophysical Prospecting

The analysis of travel times with moveout velocities represents one of the most widely used seismic signal processing techniques for the exploration and monitoring of oil and gas reservoirs. In travel time analysis for anisotropic elastic media with fractures, the knowledge of the conversion point at interfaces with incident longitudinal and reflec...

The analysis of travel times with move-out velocities represents one of the most widely used seismic signal processing techniques for the exploration and monitoring of Oil and Gas reservoirs. In travel time analysis for anisotropic elastic media with fractures, the knowledge of the conversion point at interfaces with incident longitudinal, and refl...

We have performed for the strontium ruthenate compound, a disordered tight-binding numerical study in the unitary and intermedia scattering regimes analyzing the imaginary part of the self-consistent elastic scattering cross-section at zero temperature as a function of the superconducting gap parameter using the anisotropic limit of the γ sheet. We...

We have performed a tight-binding (TB) numerical study of the unitary regime as a function of the energy gap parameter at zero temperature (Δγ0 ) in the imaginary part of the self-consistent elastic scattering cross-section (SCCS at T = 0 K) for the superconducting triplet compound strontium ruthenate in the anisotropic limit of the FS γ-sheet. We...

By comparing the experimental results obtained in the study of the electron transport and magnetic properties of samples of lightly doped strontium substituted lanthanum cuprates and the results of the theoretical analysis in the reduced elastic scattering space (RPS), we constructed the classical self-consistent strong-binding energy density profi...

Certificate of Editorial Board Membership: International Journal of Applied Mathemathics and Theorerical Physics IJAMTP - SciencePG

We use the idea of the Wigner probability distribution (WPD) in a reduced scattering phase space (RPS) for the elastic scattering cross-section, with the help of a Tight-Binding (TB) numerical procedure allowing us to consider the anisotropic quantum effects, to phenomenologically predict several phases in these two novel unconventional superconduc...

We use the idea of the Wigner probability distribution (WPD) in a reduced scattering phase space (RPS) for the elastic scattering cross-section, with the help of a Tight-Binding (TB) numerical procedure allowing us to consider the anisotropic quantum effects, to phenomenologically predict several phases in these two novel unconventional superconduc...

We compare the quasiparticle lifetime behavior in the unitary limit of two unconventional superconductors dressed by nonmagnetic impurity scattering to differentiate an anomalous functional behavior in its shape when the disorder concentration is changed in a triplet paired model with respect to the well behave singlet model. For singlet paired sup...

Inspired by the physics of the Miyake-Narikiyo model (MN) for superconductivity in the γ sheet of Sr2RuO4, we set out to investigate numerically the behavior caused by a non-magnetic disorder in the imaginary part of the elastic scattering matrix for an anisotropic tight-binding model. We perform simulations by going from the Unitary to the Born sc...

Resumen/Abstract accepted September 2008. Conference to be held in Pereira Colombia, South America.

We compare the quasiparticle lifetime behavior in the unitary limit of two unconventional superconductors dressed by nonmagnetic impurity scattering to differentiate an anomalous functional behavior in its shape when the disorder concentration is changed in a triplet paired model with respect to the well behave singlet model. For singlet paired sup...

Review Contributed to the Journal of Physics and Chemistry of Solids

We perform a numerical study of the unitary regime as a function of disorder concentration in the imaginary part of the elastic scattering cross-section for the compound Sr2RuO4 in the flat band non-disperse limit. By using a self-consistent tight-binding (TB) method, we find a couple of families of Wigner probabilistic functions that help to expla...

We perform a numerical study of the unitary regime as a function of disorder concentration in the imaginary part of the elastic scattering cross-section for the compound $Sr_2RuO_4$ in the flat band non-disperse limit. By using a self-consistent tight-binding (TB) method, we find a couple of families of Wigner probabilistic functions that help to e...

In this work, the behavior of magnetohydrodynamic waves in optically thin plasmas considering dissipative processes, thermal and magnetic diffusion, a given ionization, and the heating and cooling functions are investigated for several particular cases. A numerical eigenvalues analysis of the dimensionless secular equations according to various cas...

We compare the quasiparticle lifetime behavior in the unitary limit of two unconventional superconductors dressed by non-magnetic impurity scattering to differentiate an anomalous functional behavior in its shape when the disorder concentration is changed in a triplet paired model with respect to the well behave singlet model. For singlet paired su...

Inspired by the physics of the Miyake - Narikiyo model (MN) for superconductivity in the γ sheet of Sr2RuO4, we set out to investigate numerically the behavior caused by a non-magnetic disorder in the imaginary part of the elastic scattering matrix for an anisotropic tight-binding model. We perform simulations by going from the Unitary to the Born...

In this short review, some bulk threshold phenomena of the unconventional superconductivity in the strontium ruthenate compound (Sr2RuO4) are mentioned. Particularly, in Sr2RuO4, the Ehrenfest relations , the velocity propagation of the elastic field modes, and the ultrasound attenuation find a common point to study elastic anisotropic lattice fiel...

Inspired by the studies on the influence of transition metal impurities in high Tc superconductors and what is already known about nonmagnetic suppression of Tc in unconventional superconductors, we set out to investigate the behavior of the nonmagnetic disordered elastic scattering for a realistic 2D anisotropic high Tc superconductor with line no...

Inspired by the studies on the influence of transition metal impurities in high Tc superconductors and what is already known about nonmagnetic suppression of Tc in unconventional superconductors, we set out to investigate the behavior of the nonmagnetic disordered elastic scattering for a realistic 2D anisotropic high Tc superconductor with line no...

For pedagogical purposes, we have analyzed the relation of the total densities of states (TDOS/PDOS/OPDOS) and molecular orbital diagrams (MOD) for single and isolated molecules of Water and Nitrogen. We used the calculation level HF/6-311G, spreading the energy eigenvalues around the TDOS spikes and using the Mulliken visual analysis in Multiwfn t...

We have analyzed with pedagogical purposes the relation of the total densities of states (TDOS/PDOS/OPDOS) and molecular orbital diagrams (MOD) for single and isolated molecules of Water and Nitrogen. We use a calculation level HF/6-311G, spreading the energy eigenvalues around the TDOS spikes and using the Mulliken visual analysis in Multiwfn to s...

In this work, the behaviour of magneto-hydrodynamic waves in optically thin plasmas considering dissipative processes, thermal and magnetic diffusion, a given ionization, and the heating and cooling functions are investigated for several particular cases. A numerical eigenvalues analysis of the dimensionless secular equations according to various c...

Esta charla es un recuento del trabajo en anisotropía sísmica hecho mayormente en Intevep S.A. PDVSA en colaboración con el CWP de la Escuela de Minas de Colorado, durante los años 1995 - 2000 y 2007 - 2010. Todos compartimos la idea de que el subsuelo terrestre necesita de la anisotropía sísmica para una mejor definición de los eventos relacionad...

The analysis of travel times with normal move-out (NMO) velocities represents one of the most widely used seismic signal processing techniques. In the travel time analysis for anisotropic homogeneous elastic media, the knowledge of the conversion point (PS) in the analysis of seismic data acquired in multicomponent surveys is crucial for the correc...

En este trabajo se visualiza la aproximación elipsoidal para las velocidades de fase de los modos longitudinal-P, y transversales-S1 y-S2 en medios que poseen simetría monoclínica.

Using an HF/6-311G level of calculation, we have analyzed the meaning of the density of states (DOS) for a single molecule of water (H2O).

In this review, some problems of the unconventional superconductivity in Sr2RuO4 are touched. In the strontium ruthenate compound (Sr2RuO4), the Ehrenfest relations, the elastic velocity propagation, and ultrasound attenuation find a common point to study elastic lattice effects. This can turn into a new role of the spin and polarization of the tra...

GNU Pytronic is some software that Ronald is developing for technicians, engineers and electronics enthusiasts. It´s basically a tool for calculating discrete electronic components. It is developed in Python through a framework called Tkinter, it is multiplatform. It has a version for windows and another for GNU Linux. The license is GPL-V3

The very long-standing problem of sound waves propagation in fluids is reexamined. In particular, from the analysis of the wave damping in reacting gases following the work by Einstein (1929), it is found that the damping due to the chemical reactions occurs nonetheless the second (bulk) viscosity introduced by Landau and Lifshitz (1987) is zero. T...

Implementing computational boundary conditions such as perfectly matched layers (PML) does have advantages for forwarding modeling of the Earth's crust. The mathematical modeling of many physical problems encountered in industrial applications often leads to a set of linear partial differential equations, PDEs. It considerably improves the visualiz...

In this short note following a previous set of works [3, 4, 16, 17] we repeat the calculations for the jumps for the thermal expansion ασxy , the specific heat Cσxy , and the elastic compliance Sσxy xyxy in the basal plane of Sr2RuO4 . We use here the 4 th rank tensor notation because of the Voigt notation; where the stress and strain are treated d...

In this short note following a previous set of works [3, 4, 16, 17] we repeat the calculations for the jumps for the thermal expansion ασxy, the specific heat Cσxy, and the elastic compliance Sσxyxyxy in the basal plane of Sr2RuO4 . We use here the 4th rank tensor notation because of the Voigt notation; where the stress and strain are treated diffe...

This work performs a comparative numerical study of the impurity average self-frequency in an unconventional superconducting alloy with non-magnetic impurities. Two methods are used: the Levenberg-Marquardt algorithm as a nonlinear minimization problem, and a fixed-point iteration procedure. The unconventional superconducting renormalized by impuri...

In this short note, we repeat the calculations the jumps for the specific heat Cσxy, the elastic compliance Sσxyxyxy and the thermal expansion ασxy due to a shear stress σxy in the basal plane of Sr2RuO4. Henceforth we clarify some issues regarding the elastic theoretical framework suitable to explain the sound speed experiments of Lupien et al. (2...

Multi-azimuth walkaway vertical seismic profiling (VSP) is an established technique for the estimation of in situ slowness surfaces and inferring anisotropy parameters. Normally, this the technique requires the assumption of lateral homogeneity, which makes the horizontal slowness components at depths of downhole receivers equal to those measured a...

Multi-azimuth walkaway vertical seismic profiling (VSP) is an established technique for the estimation of in situ slowness surfaces and inferring anisotropy parameters. Normally, this technique requires the assumption of lateral homogeneity, which makes the horizontal slowness components at depths of downhole receivers equal to those measured at th...

In this short note, we calculate the jumps for the specific heat C$_{\sigma_{xy}}$, the elastic compliance S$_{xyxy}^{\sigma_{xy}}$ and the thermal expansion $\alpha_{\sigma_{xy}}$ due to a shear stress $\sigma_{xy}$ in the basal plane of \sr. Henceforth we clarify some issues regarding the elastic theoretical framework suitable to explain the soun...

Implementing computational boundary conditions, such as perfectly matched layers PML does have advantages for forwarding modeling of the earth's crust. The mathematical modeling of many physical problems encountered in industrial applications often leads to a system of linear partial differential equations-PDEs. It considerably improves the visuali...

Multiple vertical fracture sets, possibly combined with horizontal fine layering, produce an equivalent medium of monoclinic symmetry with a horizontal symmetry plane. Here, we show that multi component wide azimuth reflection data (combined with known vertical velocity or reflector depth) or multi-azimuth walkaway $VSP$ surveys provide enough info...

This work performs a comparative numerical study of the impurity average self-frequency \bw in an unconventional superconducting alloy with non-magnetic impurities. Two methods are used: the Levenberg-Marquardt algorithm as a non-linear minimization problem, and a fixed-point iteration procedure. The unconventional superconducting renormalized by i...

This paper gives a detailed numerical study of the superconducting electronic heat transport in the unconventional multiband superconductor Strontium Ruthenate Sr$_2$RuO$_4$. The study demostrates that a model with different nodal structures on different sheets of the Fermi surface is able to describe quantitatively experimental heat transport data...

The very long standing problem of sound waves propagation in fluids is reexamined. In particular, from the analysis of the wave damping in reacting gases following the work of Einsten \citep{Ein}, it is found that the damping due to the chemical reactions occurs nonetheless the second (bulk) viscosity introduced by Landau \& Lifshitz \citep{LL86} i...

In this work, a numerical study of the superconducting specific heat of the unconventional multiband superconductor Strontium Ruthenate is performed. Two band gaps models are employed, and the results rendered for each of them are compared. One of the models, previously proposed by one of the authors to explain the experimental temperature behavior...

In this work, after reviewing the theory of the elastic properties of strontium ruthenate, an extension suitable to explain the sound speed experiments of Lupien et. al. \protect\cite{lup2} and Clifford et. al. \protect\cite{clif1} is carried out. It is found that the discontinuity in the elastic constant C66 gives unambiguous experimental evidence...

Multiple vertical fracture sets, combined with horizontal fine layering produce an equivalent medium of orthorhombic or monoclinic symmetry. This is particularly important in fracture reservoir characterization. Fractured reservoirs are azimuthal anisotropic with respect to elastic-wave propagation. In this work we introduce an ellipsoidal approxim...

In this work, by employing Density Functional Theory, we compute and discuss some geometric and magnetic properties of the monomer, dimer and trimer of NiFe2 O4 . The calculations are performed at the UDFT/ B3LYP level of calculation, by employing the LANL2DZ effective pseudo potential. The results of the Mulliken spin densities and the spin polari...

AI and Data Science are a breakthrough in computer programming that combines lots of major subjects and topics. We intent to link topics such as applied math, and databases to address problems associated with learning machines and data science. Google search, health, oil R&D exploration, environment, atmospheric and solar physics, finance, astronom...

In this work, by employing Density Functional Theory, we compute and discuss some geometric and magnetic properties of the monomer, dimer and trimer of NiFe2 O4 . The calculations are performed at the UDFT/ B3LYP level of calculation, by employing the LANL2DZ effective pseudo potential. The results of the Mulliken spin densities and the spin polari...

In this work, after reviewing the theory of the elastic properties of Sr 2 RuO 4 , an extension suitable to explain the sound speed experiments of Lupien et al. [2] and Clifford et al. [3] is carried out. It is found that the discontinuity in the elastic constant C 66 gives unambiguous experimental evidence that the Sr 2 RuO 4 superconducting order...

The density of states is a very important concept within the solid state physics and conceptually represents the number of states per unit of energy. Since in the solid state the energy levels can be represented as a continuum the density of states can be plotted as a smooth curve. In an isolated molecule, the energy levels are discrete so the conc...

This is a pedagogical talk for the Science Faculty in the International Year of Light 2015. It covers the topic of photonic crystals and the localization of light.

Ongoing project

In this work, a numerical study of the superconducting specific heat of the unconventional multiband superconductor Strontium Ruthenate, Sr2RuO4 , is performed. Two band gaps models are employed, and the results rendered for each of them are compared. One of the models, previously proposed by one of the authors to explain the experimental temperatu...

Multiple vertical fracture sets, combined with horizontal fine layering produce an equivalent medium of orthorhombic or monoclinic symmetry. This is particular important in fracture reservoir characterization, and since natural fractures usually occur in vertical sets, fractured reservoirs are azimuthally anisotropic with respect to elastic-wave pr...

El análisis de las velocidades interválicas y los tiempos de transito representan una de las técnicas de procesamiento de señales sísmicas más usadas. El conocimiento del punto de conversión en el análisis de datos sísmicos adquiridos en el procesamiento multicomponente es crucial para la interpretación correcta de la data. En este trabajo se muest...

En este trabajo se introduce una aproximación elipsoidal para las velocidades de fase de los modos longitudinal -P, y transversales -S1 y -S2 en medios que poseen simetría monoclínica. Esta nueva aproximación es válida para ángulos polares pequeños cerca de la dirección vertical pero sin restricciones en el ángulo acimutal y para grados arbitrarios...

En este trabajo se introduce una aproximación elipsoidal para las velocidades de fase de los modos longitudinal -P, y transversales -S1 y -S2 en medios que poseen simetría monoclínica. Esta nueva aproximación es válida para ángulos polares pequeños cerca de la dirección vertical, pero sin restricciones en el ángulo acimutal y para grados arbitrario...

This paper gives a detailed numerical study of the superconducting electronic heat transport in the unconventional multiband superconductor Strontium Ruthenate Sr2RuO4. The study demonstrates that a model with different nodal structures on different sheets of the Fermi surface is able to describe quantitatively experimental heat transport data. The...

A Rashba metal is a two dimensional electron system with noncentrosymetric crystal structure. This lack of spatial symmetry gives rise to the spin‐orbit interaction term in the effective 2D Hamiltonian with an asymmetric potential which breaks both the inversion symmetry and the spin rotation symmetry. As the presence of the spin‐orbit term not lon...

A Rashba metal is a two-dimensional electron system with the noncentrosymmetric crystal structure. This lack of spatial symmetry gives rise to the spin‐orbit interaction term in the effective 2D Hamiltonian with an asymmetric potential which breaks both the inversion symmetry and the spin rotation symmetry. As the presence of the spin‐orbit term no...

En este trabajo se presenta un modelaje del subsuelo donde se considera que el mismo es elástico y anisotrópo. Mediante la utilización de la ecuación de onda elástica en dos dimen-siones para el caso de simétria polar vertical (VTI) se obtienen sismogramas sintéticos y tomas de pantalla del fenomeno ondulatorio. El esquema en diferencias finitas ut...

Se presenta un modelaje del subsuelo, donde se considera que es elástico y anisótropo, para la ecuación elástica en dos dimensiones considerando simetría polar vertical obteniendose sismogramas sinteticos. Se utiliza un modelo tipo FDTD de segundo orden con mallas desplazadas y para estableces las condiciones de frontrera se utliza la técnica de ca...

Los superconductores caracterizados por una superficie de Fermi compuesta por varias láminas metálicas, cada una de ellas con una brecha superconductora son llamados superconductores con varias bandas. Para los superconductores con varias bandas, los experimentos que miden las diferentes propiedades termodinámicas y de transporte, promedian la cont...

Este trabajo se realizó con la finalidad de corregir los problemas de saltos estáticos de alta frecuencia, presentes en los tiempos de viaje, los cuales aparecen en el procesamiento de datos sísmicos para la onda compresional (P). Este tipo de problemas, es causado por la incapacidad de modelar con exactitud la capa meteorizada, tanto por las varia...