The role of magnetoplasmons in Casimir force calculations

In this paper we review the role of magneto plasmon polaritons in the Casimir force calculations. By applying an external constant magnetic field a strong optical anisotropy is induced on two parallel slabs reducing the reflectivity and thus the Casimir force. As the external magnetic field increases, the Casimir force decreases. Thus, with an an external magnetic field the Casimir force can be controlled.The calculations are done in the Voigt configuration where the magnetic field is parallel to the slabs. In this configuration the reflection coefficients for TE and TM modes do not show mode conversion.Comment: contribution to QFEXT09, Norman, Oklahoma 200

Pull-in control due to Casimir forces using external magnetic fields

We present a theoretical calculation of the pull-in control in capacitive micro switches actuated by Casimir forces, using external magnetic fields. The external magnetic fields induces an optical anisotropy due to the excitation of magneto plasmons, that reduces the Casimir force. The calculations are performed in the Voigt configuration, and the results show that as the magnetic field increases the system becomes more stable. The detachment length for a cantilever is also calculated for a cantilever, showing that it increases with increasing magnetic field. At the pull-in separation, the stiffness of the system decreases with increasing magnetic field.Comment: accepted for publication in App. Phys. Let

Van der Waals torque induced by external magnetic fields

We present a method for inducing and controlling van der Waals torques between two parallel slabs using a constant magnetic field. The torque is calculated using the Barash theory of dispersive torques. In III-IV semiconductors such as $InSb$, the effect of an external magnetic field is to induce an optical anisotropy, in an otherwise isotropic material, that will in turn induce a torque. The calculations of the torque are done in the Voigt configuration, with the magnetic field parallel to the surface of the slabs. As a case study we consider a slab made of calcite and a second slab made of $InSb$. In the absence of magnetic field there is no torque. As the magnetic field increases, the optical anisotropy of $InSb$ increases and the torque becomes different from zero, increasing with the magnetic field. The resulting torque is of the same order of magnitude as that calculated using permanent anisotropic materials when the magnetic fields is close to 1 T.Comment: to appear in Journal of Applied Physic

A theoretical analysis of the role of defects in the adsorption of hydrogen sulfide on graphene

Density functional theory studies are reported to analyze the interaction between hydrogen sulfide (H2S) and graphene. The electron-ion interactions have been modeled using ultrasoft pseudopotentials and the exchange-correlation energies have been approximated by the method of the generalized gradient approximation in the parameterization of Perdew-Burke-Ernzerhof. Three graphene structures, one intrinsic and two with defects (vacancy and sustitution), and four H2S concentrations have been studied. The optimal geometries, binding energies, density of states (DOS) and charge density were obtained. In order to study the adsorption process three high symmetry sites were considered, namely, top, bridge, and center. The preferential adsorption structure corresponds to the center site in a physical way. The DOS of graphene-H2S systems shows a metallic behavior which coincides with the behavior of the isolated graphene. The geometrical structure of the graphene and the hydrogen sulfide remains unchanged

Nanoestructuras unidimensionales autoensambladas en superficies de si (001)

Diferentes tipos de nanoestructuras unidimensionales que pueden autoensamblarse en superficies de semiconductores se han estudiado experimental y teóricamente en los últimos años. Estos sistemas son interesantes no sólo por sus posibles aplicaciones, sino también desde un punto de vista fundamental. En la investigación básica el interés está motivado por la posibilidad de comprender interesantes fenómenos físicos que están relacionados con estos sistemas, tales como estabilidad de la superficie, el crecimiento y las propiedades de los sistemas de una sola dimensión, para mencionar sólo unos pocos. Para las aplicaciones tecnológicas, son muy importantes en la nanoelectrónica, ya que siempre hay una búsqueda de métodos para fabricar circuitos más pequeños (por debajo de las decenas de nanómetros), más allá de las capacidades de litografía normal. En este artículo haremos una revisión de algunos de estos sistemas, crecidos en la superficie Si(001).Different kinds of one dimensional nanostructures that self assemble on semiconductor surfaces have been studied experimental and theoretically in recent years. They are interesting not only because of possible applications but also from a fundamental point of view. In basic research the interest is motivated by the possibility to understand interesting physical phenomena that are related to these systems, such as surface stability, growth, and the properties of one-dimensional systems, to mention only a few. For technological applications, they are very important in nanoelectronics, since there is always a search for ways of creating smaller circuits (in the lower tens of nanometers), beyond the capabilities of normal lithography. In this article, we survey some of such systems when grown on the Si(001) surface