Pseudospin Splitting of the Energy Spectrum of Planar Polytype Graphene-Based Superlattices

The energy spectrum of planar polytype graphene-based superlattices has been investigated. It is shown that their energy spectrum undergoes pseudospin splitting due to the asymmetry of quantum wells forming the superlattice potential profile.Comment: 5 pages, 3 figure

Flujo sobre obstrucciones complejas

Tanto en la ingeniería como en la naturaleza existen flujos que se desplazan a través de arreglos más o menos regulares de un número elevado de elementos. A este tipo de problemas que cubre un amplio rango de escalas se lo denomina de obstrucciones complejas. Esto ha llevado en general a que el modelado de este tipo de problemas se realice dividiendo el problema en dos escalas, la escala mesoscópica y la escala macroscópica. En nuestro grupo hemos trabajado en el tema de flujos que involucran obstrucciones complejas y en los últimos años hemos estado desarrollando un sistema de Velocimetría por Imágenes de Partículas que, en combinación con la técnica de anemometría térmica utilizada en los trabajos anteriores, nos permitirá mejorar los resultados experimentales obtenidos hasta el momento. El primer trabajo a desarrollar es la caracterización del funcionamiento de los anemómetros de hilo caliente en flujos a través de medios permeables. Esto permitirá en lo sucesivo conocer las posibilidades y limitaciones de este instrumento para el tipo de problemas de interés. Por otro lado, contando ahora con mejores herramientas experimentales y numéricas, se espera volver a estudiar el problema de inestabilidad de los flujos sobre obstrucciones complejas. Se propone estudiar experimentalmente la transición en este tipo de flujos más en detalle, obteniendo para cada caso un campo de velocidades detallado para la condición de estabilidad neutra. Finalmente se espera poder realizar un análisis, al menos preliminar, de las características del flujo al comienzo y al final de una obstrucción compleja y las estructuras fluidodinámicas que se orifinan aguas abajo.Both in engineering and in nature there are flows which move through more or less regular arrangements of a large number of elements. This type of problem, in which a wide range of scales is covered, is called complex obstructions. This has led in general to model this type of problem by dividing it into two scales, the mesoscopic scale and the macroscopic scale. In our group we have worked on the subject of flows involving complex obstructions and in recent years have developed a system of particle image Velocimetry that, in combination with the technique of thermal anemometry used in previous works, will allow us to improve the experimental results that we have obtained so far. The first work to be developed is the characterization of the operation of hot wire anemometers in a flow through permeable media. This will enable us to know the possibilities and limitations of this instrument for the type of problems of interest. On the other hand, counting now with better experimental and numerical tools, we hope to revisit the problem of the instability of obstacles over complex obstructions. It is proposed to experimentally study the transition in this type of situation in more detail, obtaining for each case a detailed velocity field for the neutral stability condition. Finally, it is expected to be able to perform an analysis, at least preliminary, of the flow characteristics at the beginning and at the end of a complex obstruction and the fluid-dynamic structures that are originated downstream

Plasmons in a Planar Graphene Superlattice

Plasmon collective excitations are studied in a planar graphene superlattice formed by periodically alternating regions of gapless graphene and of its gapped modification. The plasmon dispersion law is determined both for the quasi-one-dimensional case (the Fermi level is located within the minigap) and for the quasi-two-dimensional case (the Fermi level is located within the miniband). The problem concerning the absorption of modulated electromagnetic radiation at the excitation of plasmons is also considered.Comment: 7 pages, 3 figure