Orbital Kerr effect and terahertz detection via the nonlinear Hall effect

We investigate the optical response induced by a d.c. current flowing in a nonmagnetic material that lacks inversion symmetry. In this class of materials, the flowing current experiences a nonlinear Hall effect and induces a nonequilibrium orbital magnetization, even in the absence of spin-orbit coupling. As a result, an orbital-driven Kerr effect arises that can be used to probe not only the orbital magnetization, but also the nonlinear Hall effect. In addition, in the long wavelength limit, the nonlinear Hall effect leads to a rectification current that can be used to detect terahertz radiation. We apply the theory to selected model systems, such as WTe$_2$ bilayer, as well as to realistic materials, i.e., bulk Te and metallic superlattices. The nonequilibrium orbital Kerr efficiencies obtained in these systems are comparable to the largest values reported experimentally in GaAs and MoS$_2$, exceeding the values reported in metals and suggesting a large terahertz current responsivity.Comment: 11 pages, 8 figure

Spin-orbit torque for field-free switching in C_{3v} crystals

Spin-orbit torques in noncentrosymmetric polycrystalline magnetic heterostructures are usually described in terms of field-like and damping-like torques. However, materials with a lower symmetry point group can exhibit torques whose behavior substantially deviates from the conventional ones. In particular, based on symmetry arguments it was recently proposed that systems belonging to the C_{3v} point group display spin-orbit torques that can promote field-free switching [Liu et al. Nature Nanotechnology 16, 277 (2021)]. In the present work, we analyze the general form of the torques expected in C3v crystals using the Invariant Theory. We uncover several new components that arise from the coexistence of the three-fold rotation and mirror symmetries. Using both tight binding model and first principles simulations, we show that these unconventional torque components arise from the onset of trigonal warping of the Fermi surface and can be as large as the damping-like torque. In other words, the Fermi surface warping is a key indicator to the onset of field-free switching in low symmetry crystals

Electronic and spin transport in Bismuthene with magnetic impurities

Topological insulators have remained as candidates for future electronic devices since their first experimental realization in the past decade. The existence of topologically protected edge states could be exploited to generate a robust platform and develop quantum computers. In this work we explore the role of magnetic impurities in the transport properties of topological insulators, in particular, we study the effect on the edge states conductivity. By means of realistic $\it{ab}$ $\it{initio}$ calculations we simulate the interaction between magnetic adatoms and topological insulators, furthermore, our main goal is to obtain the transport properties for large samples as it would be possible to localize edge states at large scales

Transformación Digital y Gestión Pedagógica Docente en dos instituciones educativas públicas, Pucallpa. Ucayali, 2023

El presente trabajo de investigación estudió la transformación digital y la gestión pedagógica docente, como objetivo se planteó determinar la influencia de la transformación digital en la gestión pedagógica docente. La metodología del presente trabajo tiene como tipo de investigación aplicada, nivel explicativo, enfoque cuantitativo, método hipotético-deductivo y diseño no- experimental. La población estuvo conformada por 117 docentes de dos instituciones educativas públicas y la muestra conformada por 90. La técnica de recopilación de datos para las dos variables fue la encuesta y el cuestionario se utilizó como instrumento, lo que fue validado por expertos y su confiabilidad fue dada por el coeficiente de Alfa de Cronbach. Los resultados obtenidos luego de realizar la prueba de regresión Logística Ordinal arrojaron un p-valor= 0,037 menor a 0,05, rechazando la hipótesis nula, probando que la transformación digital tiene relación significativa con la gestión pedagógica docente, obteniendo un Pseudo R2 de Cox y Snell de 44,2 % y de Nagelkerke de 44,3 %, concluyendo que la transformación digital influye significativamente en la gestión pedagógica docente de instituciones educativas públicas, Pucallpa. Ucayali

Electronic transport properties of MoS2_2 nanoribbons embedded on butadiene solvent

Transition metal dichalcogenides (TMDCs) are promising materials for applications in nanoelectronics and correlated fields, where their metallic edge states play a fundamental role in the electronic transport. In this work, we investigate the transport properties of MoS$_2$ zigzag nanoribbons under a butadiene (C$_4$H$_6$) atmosphere, as this compound has been used to obtain MoS$_2$ flakes by exfoliation. We use density functional theory combined with non-equilibrium Green's function techniques, in a methodology contemplating disorder and different coverages. Our results indicate a strong modulation of the TMDC electronic transport properties driven by butadiene molecules anchored at their edges, producing the suppression of currents due to a backscattering process. Our results indicate a high sensitivity of the TMDC edge states. Thus, the mechanisms used to reduce the dimensionality of MoS$_2$ considerably modify its transport properties

Orbital Pumping by Magnetization Dynamics in Ferromagnets

We show that dynamics of the magnetization in ferromagnets can pump the orbital angular momentum, which we denote by orbital pumping. This is the reciprocal phenomenon to the orbital torque that induces magnetization dynamics by the orbital angular momentum in non-equilibrium. The orbital pumping is analogous to the spin pumping established in spintronics but requires the spin-orbit coupling for the orbital angular momentum to interact with the magnetization. We develop a formalism that describes the generation of the orbital angular momentum by magnetization dynamics within the adiabatic perturbation theory. Based on this, we perform first-principles calculation of the orbital pumping in prototypical $3d$ ferromagnets, Fe, Co, and Ni. The results show that the ratio between the orbital pumping and the spin pumping ranges from 5 to 15 percents, being smallest in Fe and largest in Ni. This implies that ferromagnetic Ni is a good candidate for measuring the orbital pumping. Implications of our results on experiments are also discussed

Desenlaces neonatales adversos en gestantes con preeclampsia severa y sus factores asociados

Objetivo: Analizar cuáles son los desenlaces neonatales adversos que con mayor frecuencia afectan a los recién nacidos de gestantes diagnosticadas con preeclampsia severa y determinar cuáles son sus factores asociados. Material y métodos: Siguiendo un diseño de cohortes se analizaron retrospectivamente todos los casos de preeclampsia severa diagnosticados en el Instituto Nacional Materno Perinatal durante el periodo 2016-2017. Resultados: Se analizaron un total de 942 casos de preeclampsia severa (28,5 ± 7,6 años de edad). El 100% de los gestantes dio a luz a producto vivo con 36,2 ± 3,2 semanas de gestación (rango: 24-41). Los desenlaces neonatales adversos más frecuentes fueron parto pretérmino (incidencia [I]=48,7%; intervalo de confianza al 95% [IC 95%]: 45,4% a 51,9%), talla baja para edad gestacional (I=33,7%; IC 95%: 30,6% a 36,7%), pequeño para la edad gestacional (I=25,6%; IC 95%: 22,9% a 28,5%) y Apgar 1-5´ bajo al nacer (I=12,1%; IC 95%: 10,0% a 14,2%). Las gestantes adolescentes tuvieron un menor riesgo de parto prematuro (IRR =0,70; IC 95%: 0,57 a 0,85) y un puntaje Apgar 1-5´ bajo al nacer (IRR =0,39; IC 95%: 0,21 a 0,72) que las adultas. Conclusión: La incidencia de desenlaces neonatales adversos en gestantes diagnosticadas con preeclampsia severa es alta, siendo los más frecuentes prematuridad, talla baja para edad gestacional, pequeño para la edad gestacional y APGAR 1-5´ bajo al nacer. Adicionalmente, se encontró que el riesgo de parto prematuro y Apgar bajo al nacer era menor en gestantes adolescentes que en gestantes adultas