Interlayer hybridization and moir\'e superlattice minibands for electrons and excitons in heterobilayers of transition-metal dichalcogenides

Geometrical moir\'e patterns, generic for almost aligned bilayers of two-dimensional (2D) crystals with similar lattice structure but slightly different lattice constants, lead to zone folding and miniband formation for electronic states. Here, we show that moir\'e superlattice (mSL) effects in $\mathrm{MoSe}_2/\mathrm{WS}_2$ and $\mathrm{MoTe}_2/\mathrm{MoSe}_2$ heterobilayers that feature alignment of the band edges are enhanced by resonant interlayer hybridization, and anticipate similar features in twisted homobilayers of TMDs, including examples of narrow minibands close to the actual band edges. Such hybridization determines the optical activity of interlayer excitons in transition-metal dichalcogenide (TMD) heterostructures, as well as energy shifts in the exciton spectrum. We show that the resonantly hybridized exciton (hX) energy should display a sharp modulation as a function of the interlayer twist angle, accompanied by additional spectral features caused by umklapp electron-photon interactions with the mSL. We analyze the appearance of resonantly enhanced mSL features in absorption and emission of light by the interlayer exciton hybridization with both intralayer A and B excitons in $\mathrm{MoSe}_2/\mathrm{WS}_2$, $\mathrm{MoTe}_2/\mathrm{MoSe}_2$, $\mathrm{MoSe}_2/\mathrm{MoS}_2$, $\mathrm{WS}_2/\mathrm{MoS}_2$, and $\mathrm{WSe}_2/\mathrm{MoSe}_2$.Comment: Final published version, with updated title and abstract, minor corrections to equations, and 4 new figures adde

Simulation and tests for the characterization of the response of the detection system fora UAV system

The present thesis project consisted in the testing of a gamma rays and neutron detectormounted on an UAV (Unmanned Aerial Vehicle). The detector is a CLLB (Cs2LiLaBr6), which is a gamma-neutron scintillation detector. This one was tested separately in order to determine its response to different gamma radiation sources in different conditions. After the experiments with the gamma sources, neutron sources were employed in order to test the neutron detection and capability of the CLLB. The detection system (CLLB detector + digitizer) was mounted in the drone (UAV) for a simulation of a typical surveillance flight of the UAV, and again to observe and analyze the detection response before a gamma source in motion. For each test with the gamma sources, simulations of the detector and its features were performed with the software GEANT4 in order to compare them with the results obtained experimentally. Additionally, experiments with silicon photomultipliers (SiPM) coupled to CsI and SrI detectors were performed in order to quantify their resolution and compare the values obtained between them, and the resolution values obtained with the CLLB detector.ope

Superconductivity-induced features in electronic Raman spectrum of monolayer graphene

Using the continuum model, we investigate theoretically contribution of the low-energy electronic excitations to the Raman spectrum of superconducting monolayer graphene. We consider superconducting phases characterised by an isotropic order parameter in a single valley and find a Raman peak at a shift set by the size of the superconducting gap. The height of this peak is proportional to the square root of the gap and the third power of the Fermi level, and we estimate its quantum efficiency as $I\sim10^{-14}$.Comment: 7 pages, 2 figure

Effective algorithm of analysis of integrability via the Ziglin's method

In this paper we continue the description of the possibilities to use numerical simulations for mathematically rigorous computer assisted analysis of integrability of dynamical systems. We sketch some of the algebraic methods of studying the integrability and present a constructive algorithm issued from the Ziglin's approach. We provide some examples of successful applications of the constructed algorithm to physical systems.Comment: a figure added, version accepted to JDC

Sistemas de detección de ironía basados en palabras y caracteres para textos cortos en español

La ironía verbal es un fenómeno lingüístico en donde el significado expresado es el opuesto al significado literal del mensaje. Es un reto para el Procesamiento de Lenguaje Natural ya que se debe enseñar a un sistema una forma de reconocer y procesar el cambio de polaridad de lo expresado. Aun cuando han habido esfuerzos recientes en la identificación de ironía y sarcasmo, ninguno de estos aborda el problema en español. En este trabajo nos enfocamos en establecer un sistema base de clasificación usando características simples al nivel de palabras y caracteres para entradas en español de la red social Twitter. Presentamos sistemas basados en máquinas de soporte vectorial y selvas aleatorias usando n-gramas, así como un enfoque distribucional (i.e., word2vec).Verbal irony is the linguistic phenomenon in which the expressed meaning is the opposite of the literal meaning. Irony is a challenging task for Natural Language Processing, since one must teach a system to identify and process the polarity of the expression. Although there have been recent efforts in irony and sarcasm identification, none of them tackle the issue in Spanish. In this work we focus on producing classification baseline systems using straight-forward word and character features for Spanish posts from the social network Twitter. We present a set of n-gram baselines using support vector machines and random forests classifiers, as well as for a distributional approach (i.e., word2vec).Authors thank Red Temática en Tecnologías del Lenguaje CONACyT for the support provided to the first author during part of this research

Elementary equivalence of right-angled Coxeter groups and graph products of finite abelian groups

We show that graph products of finite abelian groups are elementarily equivalent if and only if they are $\exists\forall$-equivalent if and only if they are isomorphic. In particular, two right-angled Coxeter groups are elementarily equivalent if and only if they are isomorphic.Comment: 7 pages; version 2: added a reference to David Radcliffe's rigidity result and Remark 2.

Análisis jurídico de los retos y compromisos emanados del Protocolo del Tratado General de Integración Económica Centroamericana y su relación con el Acuerdo de Asociación entre Centroamérica y la Unión Europea en su pilar comercial

Analiza los compromisos que devienen del protocolo al Tratado de Integración Económica Centroamericana y su relación con el Acuerdo de Asociación entre Centroamérica y la Unión Europea en su pilar comercial, determinando la adaptación necesaria para su materialización

Rainwater harvesting system as a strategy for adaptation on climate change: a review

In the face of increasing water scarcity aggravated by climate change, the rainwater harvesting system is a technique that increases the water supply for various purposes. The objective of this research is to analyse the recent literature published on the rainwater collection system, for which the systematic review method was used. The main form of rainwater catchment are roofs, but the material used is important because it can affect the quality of the water. Some physicochemical parameters of rainwater may be within the standards for human consumption, but it is contaminated by pathogenic microorganisms, which represents a risk to public health if it is consumed without prior treatment, so it is mainly used for irrigation and flushing toilets. However, this system has been implemented mainly in rural areas to satisfy their basic needs, including human consumption, because these places do not have access to the central drinking water system. Given this scenario, treatment technologies are being developed that are easy to operate and maintain, such as solar disinfection and filtration for drinking water purposes. This study provides a global overview progress of research related to the rainwater harvesting system