Vol. 69 No. 2 Mar-Apr (2023): Revista Mexicana de Física

It is shown that c-number elko spinors obey the massless Dirac equation and are unitarily equivalent to Weyl bispinors. Therefore, they do not constitute a new spinor type with mass dimension one.

The inspection of materials supporting topological excitations is one of the prospective areas of condensed matter physics. This paper is devoted to studying the possibility of the existence of topological phases in Na₂CuX (X= As, Sb, Sn and Bi) full Heusler compounds using the FP-LMTO (Full-Potential Linear Muffin-Tin Orbital) method with and without spin-orbit coupling (SOC). The study of structural properties has found that these materials are energetically stable in the Hg2CuTi type structure. Also, formation energy calculations have shown that these materials are convenient to manufacture. Otherwise, band structure calculations show that these materials exhibit the behavior of non-trivial topological materials with a semi-metallic nature. The obtained results in this study, generally, showed that SOC is not a primary cause of the band inversion mechanism.

The use of machine learning algorithms to address classification problems in several scientific branches has increased over the past years. In particular, the supervised learning technique with artificial neural networks has been successfully employed in classifying phases of matter. In this article, we use a fully connected feed-forward neural network to classify extended and localized single-particle states that arise from quasiperiodic one-dimensional lattices. We demonstrate that our neural network achieves to correctly uncover the nature of the single-particle states even when the wave functions come from a more complex Hamiltonian than the one used to train the network.

An update is described of a model independent method to determine the hadronic contribution to the QED running coupling at the Zboson mass scale, ∆αHAD(M2 Z ). The major source of uncertainty is from the contribution of the light quark vector current correlator at zero momentum. This uncertainty is substantially reduced using recently improved lattice QCD results for this correlator. The result is ∆αHAD(M2 Z ) = 274.13(0.73) × 10−4

Understanding the interaction between particles and matter is important for the advancement of new detection and particles properties measurement techniques. The result of interaction processes between incident particle and detection material is the production of photons, ions or both. The photon production in metal plaques due to cosmic rays incidence has not been reported to date. We planned, designed, built, characterized and operated an experimental system based on 10 × 10 cm Aluminium plates of various thicknesses and the photodiode Hamamatsu S12572-100P with which we show evidences of photon production in Aluminium due to cosmic rays incidence. We detected signals between violet and infrared with a minimum of dark counts, with approximately the same intensity, the same proportion between the different colors, and we show that they have characteristics that we associate with photons: absorption, reflection, refraction, dispersion and polarization, then we concluded that the detected signals must be produced by photons. The photons are produced inside the material by the incidence of cosmic rays. We observed that the greater the thickness of Aluminium traversed the greater the number of photons produced, in concordance with the very well known result that the greater the thickness of Aluminium traversed by the particle the greater the deposited energy. Some applications of this phenomenon are elementary particles detection, identification of materials, study of cosmic rays, study of ionizing radiation, etc. We present technical details of the experimental system, the physical results obtained, and outline possible explanations of this phenomenon.

El entendimiento de la interacción entre partículas y la materia es importante para el avance de nuevas técnicas de detección y medición de propiedades de las partículas. El resultado de los procesos de interacción partícula incidente y material de detección es la producción de fotones, de iones, o de ambos. A la fecha no se ha reportado la producción de fotones en placas metálicas por incidencia de rayos cósmicos. Planeamos, diseñamos, construimos, caracterizamos y operamos un sistema experimental, basado en placas de Aluminio de 10cm x 10cm de varios espesores y el fotodiodo Hamamatsu S12572-100P, con el que mostramos evidencias de la producción de fotones en Aluminio por incidencia de rayos cósmicos. Detectamos señales entre el violeta e infrarrojo, con un mínimo de cuentas oscuras, con aproximadamente la misma intensidad, la misma proporción, entre los diferentes colores, y mostramos que tienen características que asociamos a los fotones: absorción, reflexión, refracción, dispersión, y polarización, por lo que concluimos que deben de ser fotones las señales detectadas. Los fotones se producen en el interior del material por incidencia de rayos cósmicos. Observamos que a mayor espesor de Aluminio atravesado mayor número de fotones producidos, en concordancia con el resultado conocido que a mayor espesor de aluminio atravesado por la partícula mayor energía depositada. Algunas aplicaciones de este fenómeno son detección de partículas elementales, identificación de materiales, estudio de rayos cósmicos, estudio de radiación ionizante, etc. Presentamos los detalles técnicos del sistema experimental, los resultados físicos obtenidos, y esbozamos posibles explicaciones de este fenómeno.

We present a study of the flavor changing decays φ → tc (φ = HF, AF ) of the CP-even and CP-odd scalar flavons at the large hadron collider and its next stage, the high-luminosity large hadron collider. The theoretical framework is an extension of the standard model that incorporates an extra complex singlet and invokes the Froggatt-Nielsen mechanism with an Abelian flavor symmetry. The projected exclusion and discovery regions in terms of the model parameters are reported. We find that AF could be detected at the LHC by considering a reasonable scenario of the model parameter space. As far as HF is concerned, we also found promising results that could be verified experimentally at the high-luminosity LHC.

Europium doped and mixed with Sm₂O₃ ceramics were obtained from europium and samarium chlorides formation via citrate sol-gel route. This work reports the influence of the europium ions on the structural and luminescent properties of Sm₂O₃:Eu³⁺ ceramics (CIE coordinates) by varying the Eu³⁺ from 10 to 50 mol%. Chemical, structural, and morphological characteristics were established by FTIR and XRD, revealing the presence of characteristics Sm-O vibrational bands of a cubic structure up to 40 mol% Eu³⁺ and a phase mixture of Sm₂O₃ and Eu₂O₃ from 50 mol% Eu³⁺. The CIE coordinates values and color emission were established for Sm₂O₃:Eu³⁺ (10, 20, 30, 40 y 50 mol%) ceramics, for both, samples with a single phase and the one with mixed phases.

In this contribution, we propose a new plasmonic configuration that can be functionalized in two wavelength regimes to generate a single interface mode or multiple interface modes. The structure comprises a negative metamaterial or Left-Handed Material (LHM) coated on 2S2G-glass prism and adjacent with a sensing medium. According to the results, the negative metamaterial thickness affects significantly the potential of the structure to operate as conventional plasmonic structured formed by Fabry-Perot cavities. Additionally, we, also show that the structure can be used as a plasmonic refractive index sensor defined in the range of 1 to 1.53 refractive index unit (RIU) where the full width at half maximum (FWHM) of the SPR curve on the characteristic’s manipulation such that FWHM of p-reflectivity decreases for thick LHM layer. To understand the obtained results, the optical response from the proposed waveguide was numerically predicted by the use of the transfer matrix method (TMM) and Fresnel’s theory. In addition, the potentials of the designed waveguide as an optical modulator and Fabry-Perot interferometer are also presented.

Cerium polymeric composites have novel applications in fuel cells, optical devices, gas sensors, catalysis, ultraviolet absorbers, hydrogen storage materials, and biomedicines. This study reports the fabrication of low-cost electrospun single and core-shell polyethylene oxide (PEO) doped with Cerium fibers fabricated in two moisture ambients. Scanning electron microscopy and atomic force microscopy revealed that obtaining the thinnest average fiber diameter requires 47-52 %RH and 2 % Cerium dopant. Using a PEO capping (shell fiber) allows the increment of Cerium in the inner matrix (core-fiber) to produce non-beading continuous fibers with 3.5% of the dopant. The undoped single or core-shell fibers presented a 52.7 to 54.2 % crystallinity, indecently of relative humidity used during the fabrication process. In contrast, the use of Cerium dopant up to 2% induces an increase in their crystallinity due to the formation of Ce-O species, enhancing their thermal properties, regardless of the moisture during manufacturing as was found with Fourier transform infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analysis.

Motivating by examining the break-up effect of ⁷Li projectile into t + α cluster structure in the field of ⁵⁸Ni nucleus, the available experimental angular distributions for ⁷Li + ⁵⁸Ni elastic scattering system at energies ranging from 13 and up to 42 MeV are studied utilizing different phenomenological as well as microscopic potentials. Data analysis utilizing the Sao Paulo potential revealed that in order to reproduce the data, the strength of the real folded potential had to be reduced by ~ 36 %. While, data analysis utilizing the double folding CDM3Y6 potential with and without the rearrangement term revealed that the potential strength needed to be reduced by ~ 63 and 62 %, respectively. Cluster folding model based on the t + α cluster structure for ⁷Li is applied to reproduce the considered data. Similar results were obtained showing the necessity to reduce real cluster folding potential strength by about 49 %. The reported reduction in potential strength from the different implemented potentials supports the strong ⁷Li break-up impact. Finally, the full microscopic continuum discretized coupled channels approach is applied with a great success in reproducing the considered data.    

We investigate for the first time, photorefractive solitons in a two photon photorefractive waveguide which also exhibits the bulk photovoltaic effect. The dynamical evolution equation of such solitons has been obtained under the paraxial ray approximation along with the Wentzel-Kramers-Brilluoin Jefferys (WKBJ) approximation. The existence curve for the solitons is derived and four distinct regions of power have been identified in the absence of waveguiding depending upon the threshold power for self trapping. Bistable states have been observed to be present. We have studied the effect of the planar waveguide and found that it enhances the self trapping nonlinearity and hence results in a reduction of the threshold power required for formation of the soliton. The propagation of the light beam is studied for various different strengths of the waveguide. A beam which would not have normally been self trapped can now become a soliton by virtue of the planar waveguide structure. Finally, we investigate the linear stability of these solitons by both, the Lyapunov method and numerical simulations.

This paper presents preliminary results of Dy₂(CO₃)₃→Dy₂O₃ transition have been successfully obtained by Chemical Bath Deposition technical and subsequent thermal annealing temperature at ~600 °C. Two different temperatures of ~20°C and ~90 °C ± 2 °C are chosen to carry out the nanocrystalline growth. The crystalline phase is investigated by applying X-Ray Diffraction (XRD) and some optical properties; Transmittance, Reflectivity, Normalized Absorbance, real (n) and imaginary (k) parts refractive index. The crystalline phase of these inorganic nanomaterials for Dy₂(CO₃)₃ is orthorhombic phase, while for Dy₂O₃ it is cubic. Grain size average values located at ranged ~2.8-3.4 nm for Dy₂(CO₃)₃ and ~6.5-9.6 nm for Dy₂O₃. Vibrational modes are identified by Raman spectroscopy, modes at ~150-1800 cm^-1 frequency range assigned to internal vibrations of  ion: v₁-symmetric stretching (~1098 cm^-1) v₃-asymmetric -C-O stretching situated at ∼1063 cm^-1, were observed corresponding to orthorhombic crystalline phase. The F_g+ A_g and A_1g modes, corresponding to cubic phase Dy₂O₃. Multiple absorption bands with different relative intensities are observed at UV-Vis-NIR region, assigned to 4fs→4fs intra-electronic transitions and band gap energy. Absorption measurement were assigned to the transitions from ground state (⁶H_15/2) to different excited states such as ⁴I_13/2→⁴F_7/2, ⁴I_15/2, ⁶F_3/2, ⁶F_5/2, ⁶F_7/2→⁶H_5/2, ⁶F_9/2→⁶H_7/2, ⁶F_11/2→⁶H_9/2 and ⁶H_11/2 of Dy³⁺ cation. Tauc’s plot reveals band gap situated at range ~4.66-5.17 eV for Dy₂(CO₃)₃ and ~4.26-4.80 eV for Dy₂O₃ respectively.

Optical coupling gratings are strategic components of integrated optics that allow the interaction of a laser signal with optical interconnects, integrated photonic microdevices and biosensors. In this work, the design of binary and sinusoidal type coupling gratings for Al2O3/SiO2/Si submicron guides operating in the visible (633 nm) and infrared (1550 nm) is presented herein. In particular, the coupling efficiency is analyzed as a function of the main design parameters: waveguide thickness, period, etch depth and incidence angle. The results indicate that coupling efficiencies of 21 and 15 percent and decoupling efficiencies of 25 and 22 percent can be obtained for binary and sinusoidal gratings, respectively, at a wavelength of 1550 nm; coupling efficiencies of 7.8 and 7.6 percent and decoupling efficiencies of 53 and 34 percent can be obtained for a wavelength of 633 nm. The proposed designs have potential applications for the fabrication of integrated circuits.

Zinc oxide (ZnO _(s) ) is prepared by Chemical Bath Deposition. This manuscript continues with previous research examining the Photoluminiecence  at UV-Vis-region.   According to emission bands situated at Vis-region by means of Photoluminescence, green (GE) and yellow emission (YE) bands are discussed, which are associated with native intrinsic crystalline defects. The Photoluminescence dependence with the trap density and the surface recombination velocity in the light of the Maxwell-Boltzmann theoretical model (MBM) results associated with the electronic transitions related to the native intrinsic defects situated at9 Vis-region are investigated. The trap density (cm ^-1 ) of nanocrystals located at range ~8.9-9.9  An approximate a theoretical-experimental kinetic model is presented, considering that the coordination complex ion is a key parameter in the crystal growth of ZnO _(s) nanocrystals. The optimized geometry of [Zn(NH ₃ ) ₄ ] ²⁺ molecule was obtained with the DFT method using the functional of H-GGA B3LYP.

In this research paper, we have utilized the Jacobi elliptic function expansion method to obtain the exact solutions of (1+1)- dimensional Boussinesq System (GBQS). The most important difference that distinguishes this method from other methods is the parameters included in the auxiliary equation F’ (ξ) =  Ö P F4(ξ) + QF2(ξ) + R. As far as the authors know, there is no other study in which such a variety of solutions has been given. Depending on P, Q and R, nineteen the solitary wave and periodic wave solutions are obtained at their limit conditions. In addition, 3D and contour plot graphics for the constructed waves are investigated with the computer package program by giving special values to the parameters involved. The validity and reliability of the method is examined by its applications on a class of nonlinear evolution equations of special interest in nonlinear mathematical physics. The results were acquired to verify that the recommended method is applicable and reliable for the analytic treatment of a wide application of nonlinear phenomena

The air pollution due to tropospheric ozone (O₃) is one of the most serious problems of large industrialized cities in the world. The excessive increase in O₃ has a negative impact on the population health. Consequently, researchers have focused their efforts establishing measures to characterize the statistical analysis of spatio-temporal data. This work shows a study based on seasonal analysis of spatio-temporal data through second order structure function to and the scale behavior in power law by using the Hurst exponent (H) and analyzing the trend of fluctuations associated with O₃ pollution concentration records at four monitoring stations in the Metropolitan Area of Mexico City (MAMC) considering the four season of the year. The records were consulted from the database of the Automatic Atmospheric Monitoring Network (AAMN) in Mexico City from 2010 to 2018. The results show the differences in behavior of ozone according to the seasons of the year in this megacity. The behavior of statistical persistence predominates in spring, with 63.89% of occurrence over the total of the samples analyzed. In winter, the observed regime is antipersistent, with 80.56%. The three regimes: persistence, randomness and antipersistence were observed in summer and autumn, with a similar proportion of occurrence of 33% ± 3%. Given the above, the climatological characteristics of each season could be associated with the regimes of persistent, random and antipersistent behavior of the fluctuation of the concentration of the pollutant O₃

The dissipative motion and the rise of a heavy symmetrical top with a hemispherical peg are studied. A model taking the fixed point of the top as the center of the peg is considered when the top completely slips and the rolling motion is ignored. This is different from existing models like Jellet's one. Jellett's model and pure slipping are compared for different tops for the rise of the top, and an experimental method to determine the better model is proposed.

The quality of thin films represents the key to any improvement made in the device components manufacturing, and the way to obtain this quality based on deposition parameters takes the attention of our group. In this work, using the sputtering technique in the context of the Monte-Carlo approximation, an investigation of the effect of temperature and elevated pressure on the number of ejected particles and hence their deposition and the creation of finest thin films are applied. A vacuum chamber with 30x30x50 cm in dimension holding a magnetron which has a 2 cm in radius circular target was created. Inside this chamber, 105 particles of Argon (Ar) followed by the same number of xenon (Xe) gas are injected. This target moves away by 15cm from the substrate (with 7 cm in radius), containing three materials (Silicon (Si), germanium (Ge), and copper (Cu)) widely used in advanced technologies as in electronics and photovoltaic cells panels. Evident and satisfactory results were obtained, demonstrating that increasing pressure (0.5, 2, and 5 Pa) for both gases drops off in a spectacular way the total number (with different values) of the material particles reaching the substrate and disrupting the morphology of the thin films. moreover, and contrary to pressure, it has also been proved that mounting gas temperatures of 100, 300, and 600 K, representing three different states in kelvin degrees, where 100 K-173°C for the low (cold), 300 K27°C for the regular (atmospheric) and 600 K327°C for the high (warm) instances, supply a large number of materials atoms in substrate-level which conduct to the finest quality of the thin films. In addition, germanium gives the best results compared to silicon and copper.

The spin-s one dimensional Ising model is studied analytically within the framework of transfer matrix method. Exact results for some thermodynamical properties such as the internal energy, the entropy, the magnetization and the magnetic susceptibility are obtained for general spin-s in the absence (presence) of a magnetic field. The critical behavior of the thermodynamical properties are analysed for some values of spin-s (1/2, 1 and 3/2) at different temperature and field. The asymptotic behavior of these properties are investigated especially close to the critical temperature T → 0 and when T → ∞.