Author: Isaac Vargas

MIRADAS SUSPENDIDAS. LAS FOTOS DE LOS DESAPARECIDOS EN JALISCO

Isaac Vargas (2020)

"La guerra contra el crimen ha traído consigo, durante los últimos trece años, un amasijo de violencias que ha dejado profundas huellas en la sociedad mexicana. Los medios de comunicación audiovisual registran cotidianamente las expresiones de la fallida estrategia de seguridad, aunque lo hacen mayormente a partir de su estetización y espectacularidad. En medio de la cobertura por las cabeceras informativas han surgido otras prácticas realizadas por las víctimas de la guerra, sobre todo desde las familias de los desaparecidos, quienes utilizan la materialidad de la imagen para crear fichas de búsqueda que permitan visualizar la ausencia de sus seres queridos. En el presente trabajo responderé a la pregunta: ¿qué significados tiene la fotografía en el marco de la desaparición de personas en medio de la guerra contra el crimen? Para ello me basaré en el análisis y despliegue de fichas recabadas durante mi trabajo de campo en Guadalajara a lo largo de 2018 y 2019. El texto incluye entrevistas y viñetas que me permiten ilustrar de mejor manera la relevancia que cobra la foto ante el evento de la desaparición, en el cual la identidad del ausente, que trata de mostrarse ante los otros por medio de la imagen, desempeña un papel central".

Article

Desaparición. Fotografía. Identidad. Violencias. CIENCIAS SOCIALES SOCIOLOGÍA PROBLEMAS SOCIALES CRIMEN CRIMEN

Thomas–Fermi–Dirac calculations of valence band states in two p-type delta-doped ZnSe quantum wells

ISAAC RODRIGUEZ VARGAS (2005)

We present the hole sub-band structure study in two p-type δ-doped ZnSe QW’s. An analytical expression

for the Hartree–Fock potential is obtained following the lines of the Thomas–Fermi–Dirac (TFD) approximation.

We have analyzed the dependence of the hole energy levels to the impurity density and the

interlayer distance between wells. The exchange effects are also included in the present survey. We find

that many body effects cannot be ignored because these are really important in the calculation at least in

the low concentration regime. We have obtained an energy difference between the top of the valence band

and the ground energy of the heavy hole ladder of E0 = 29.0 meV 0 ( 2 791eV) g E - E = . in good agreement

with the experimental reports ( DAP E = 2.792 eV) available. We calculate the mobility ratio between

double δ-doped QW’s and simple δ-doped QW based on a phenomenological formula. We find the optimum

interlayer distance between wells for maximum mobility for three impurity concentrations, which

can be of great importance for technological applications.

Producción Científica de la Universidad Autónoma de Zacatecas UAZ

Article

CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA sub-band structure Hartree–Fock potential δ-doped technique

Self-similar transmission patterns induced by magnetic field effects in graphene

ISAAC RODRIGUEZ VARGAS (2018)

In this work we study the propagation of Dirac electrons through Cantor-like structures in graphene. In concrete,

we are considering structures with magnetic and electrostatic barriers arrange in Cantor-like fashion. The Diraclike

equation and the transfer matrix approach have been used to obtain the transmission properties. We found

self-similar patterns in the transmission probability or transmittance once the magnetic field is incorporated.

Moreover, these patterns can be connected with other ones at different scales through well-defined scaling rules.

In particular, we have found two scaling rules that become a useful tool to describe the self-similarity of our

system. The first expression is related to the generation and the second one to the length of the Cantor-like

structure. As far as we know it is the first time that a special self-similar structure in conjunction with magnetic

field effects give rise to self-similar transmission patterns. It is also important to remark that according to our

knowledge it is fundamental to break some symmetry of graphene in order to obtain self-similar transmission

properties. In fact, in our case the time-reversal symmetry is broken by the magnetic field effects.

Producción Científica de la Universidad Autónoma de Zacatecas UAZ

Article

CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA Self-similarity Scaling rules Transmittance Magnetic field Cantor structures

Giant oscillating magnetoresistance in silicene-based structures

ISAAC RODRIGUEZ VARGAS (2018)

Ballistic electron transport in a silicene structure, composed of a pair of magnetic gates, in the ferromagnetic and an-tiferromagnetic configuration is studied. This theoretical study has been done using the matrix transfer method to calculate the transmission, the conductance for parallel and antiparallel magnetic alignment and the magnetoresistance. Results show that conductance and magnetoresistance oscillate as a function of the length between the two magnetic domains. The forbidden transmission region also increases as a function of the barrier separation distance.

Producción Científica de la Universidad Autónoma de Zacatecas UAZ

Article

CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA Silicene Oscillating Magnetoresistance ferromagnetic tiferromagnetic

Refractive index changes in n-type delta-doped GaAs under hydrostatic pressure

ISAAC RODRIGUEZ VARGAS (2014)

The effect of hydrostatic pressure on the refractive index changes (RIC) is studied in δ-doped quantum well (DDQW) in GaAs. Based on the effective mass approximation we implement an algebraic formalism to calculate the electronic structure and RIC. Our results obtained with this model show that the position and the magnitude of the linear, nonlinear and total RIC are sensitive to hydrostatic pressure and bidimensional density. The incident optical intensity has a great effect on these optical quantities.

Producción Científica de la Universidad Autónoma de Zacatecas UAZ

Article

CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA Refractive index changes linear and nonlinear hydrostatic pressure δ-doped quantum wells

Subband and transport calculations in double -type -doped quantum wells in Si

ISAAC RODRIGUEZ VARGAS (2006)

The Thomas-Fermi approximation is implemented in two coupled n-type -doped quantum wells in

Si. An analytical expression for the Hartree-Fock potential is obtained in order to compute the

subband level structure. The longitudinal and transverse levels are obtained as a function of the

impurity density and the interlayer distance. The exchange-correlation effects are analyzed from an

impurity density of 8 1012 to 6.5 1013 cm−2. The transport calculations are based on a formula

for the mobility, which allows us to discern the optimum distance between wells for maximum

mobility.

Producción Científica de la Universidad Autónoma de Zacatecas UAZ

Article

CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA Thomas-Fermi approximation double n-type Hartree-Fock potential

Fano resonances in bilayer graphene superlattices

ISAAC RODRIGUEZ VARGAS (2017)

In this work, we address the ubiquitous phenomenon of Fano resonances in bilayer graphene. We consider that this phenomenon is as exotic as other phenomena in graphene because it can arise without an external extended states source or elaborate nano designs. However, there are not theoretical and/or experimental studies that report the impact of Fano resonances on the transport properties. Here, we carry out a systematic assessment of the contribution of the Fano resonances on the transport properties of bilayer graphene superlattices. Specifically, we find that by changing the number of periods, adjusting the barriers height as well as modifying the barriers and wells width it is possible to identify the contribution of Fano resonances on the conductance. Particularly, the coupling of Fano resonances with the intrinsic minibands of the superlattice gives rise to specific and identifiable changes in the conductance. Moreover, by reducing the angular range for the computation of the transport properties it is possible to obtain conductance curves with line-shapes quite similar to the Fano profile and the coupling profile between Fano resonance and miniband states. In fact, these conductance features could serve as unequivocal characteristic of the existence of Fano resonances in bilayer graphene.

Producción Científica de la Universidad Autónoma de Zacatecas UAZ

Article

CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA Fano resonances bilayer graphene transport properties

An alternative way of calculating the superlattice Green function for discrete media

ISAAC RODRIGUEZ VARGAS (2004)

We present an alternative and efficient way for calculating the superlattice Green function for discrete systems. Theidea is to consider the superlattices as a crystal with the unit cell having the size of the superlattice period in the growthdirection. The calculation method takes into account the matrix structure of the system Hamiltonian and a block tridiagonal matrix inversion algorithm. To illustrate the method we study the electronic band structure of a semiconductor superlattice described by means of an empirical sp3s tight-binding Hamiltonian, including nearest-neighbor interactions and spin–orbit coupling.

Producción Científica de la Universidad Autónoma de Zacatecas UAZ

Article

CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA Superlattices Green’s function methods Surface electronic phenomena (work function, surface potential, surface states, etc.)

Hole states in diamond p-delta-doped field effect transistors

ISAAC RODRIGUEZ VARGAS (2009)

The p-delta-doping in diamond allows to create high density two-dimensional hole gases. This technique has already been applied in the design and fabrication of diamond-based field effect transistors. Consequently, the knowledge of the electronic structure is of significant importance to understand the transport properties of diamond p-delta-doped systems. In this work the hole subbands of diamond p-type delta-doped quantum wells are studied within the framework of a local-density Thomas-Fermi-based approach for the band bending profile. The calculation incorporates an independent three-hole-band scheme and considers the effects of the

contact potential, the delta-channel to contact distance, and the ionized impurity density.

Producción Científica de la Universidad Autónoma de Zacatecas UAZ

Article

CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA p-delta-doping in diamond e high density two-dimensional hole gases local-density Thomas-Fermi-based

Self-similar conductance patterns in graphene Cantor-like structures

ISAAC RODRIGUEZ VARGAS (2017)

Graphene has proven to be an ideal system for exotic transport phenomena. In this work, we report

another exotic characteristic of the electron transport in graphene. Namely, we show that the linearregime

conductance can present self-similar patterns with well-defined scaling rules, once the graphene

sheet is subjected to Cantor-like nanostructuring. As far as we know the mentioned system is one of the

few in which a self-similar structure produces self-similar patterns on a physical property. These patterns

are analysed quantitatively, by obtaining the scaling rules that underlie them. It is worth noting that

the transport properties are an average of the dispersion channels, which makes the existence of scale

factors quite surprising. In addition, that self-similarity be manifested in the conductance opens an

excellent opportunity to test this fundamental property experimentally.

Producción Científica de la Universidad Autónoma de Zacatecas UAZ

Article

CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA electron transport in graphene conductance patterns