Fisica Teorica y Aplicada

Antioquia, Colombia

Fisica Teorica y Aplicada

Antioquia, Colombia
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Restrepo R.L.,Fisica Teorica y Aplicada | Martinez-Orozco J.C.,Autonomous University of Zacatecas | Barseghyan M.G.,Yerevan State University | Mora-Ramos M.E.,Fisica Teorica y Aplicada | And 3 more authors.
Acta Physica Polonica A | Year: 2014

Using a variational procedure within the effective mass approximation, we have calculated the hydrogenic impurity binding energy as well as the impurity-related nonlinear optical absorption in a single quantum ring with axial n-type delta-doping. The delta-like potential along the z-direction is analytically modeled with a Hartree-like conffning proffle fftted to a one-dimensional Thomas Fermi-based potential in the local density approximation. Both on-center and on-edge impurity positions are considered and the energies of the impurity states are examined as functions of the vertical size of the ring. It is found that the effect of changes in the geometry of the quantum ring leads to a shifting of the resonant peaks of the intra-band optical spectrum.


Baghramyan H.M.,Yerevan State University | Barseghyan M.G.,Yerevan State University | Kirakosyan A.A.,Yerevan State University | Restrepo R.L.,Fisica Teorica y Aplicada | And 4 more authors.
Journal of Luminescence | Year: 2014

The linear and nonlinear optical absorption associated with the transition between 1s and 2s states corresponding to the electron-donor-impurity complex in GaAs/Ga1-xAlxAs three-dimensional concentric double quantum rings are investigated. Taking into account the combined effects of hydrostatic pressure and the variation of the aluminum concentration, the energies of the ground and first excited s-like states of a donor impurity in such a system have been calculated using the effective mass approximation and a variational method. The energies of these states and the corresponding threshold energy of the optical transitions are examined as functions of hydrostatic pressure, aluminum concentration, radial impurity position, as well as the geometrical dimensions of the structure. The dependencies of the linear, nonlinear and total optical absorption coefficients as functions of the incident photon energy are investigated for different values of those mentioned parameters. It is found that the influences mentioned above lead to either redshifts or blueshifts of the resonant peaks of the optical absorption spectrum. It is particularly discussed the unusual property exhibited by the third-order nonlinear of becoming positive for photon energies below the resonant transition one. It is shown that this phenomenon is associated with the particular features of the system under study, which determine the values of the electric dipole moment matrix elements. © 2013 Elsevier B.V.


Miranda G.L.,Fisica Teorica y Aplicada | Miranda G.L.,University of Antioquia | Mora-Ramos M.E.,Fisica Teorica y Aplicada | Mora-Ramos M.E.,Autonomous University of the State of Morelos | And 2 more authors.
Physica B: Condensed Matter | Year: 2013

In this work the variations of the exciton-related optical absorption and the change of the refractive index in a GaAs-(Ga,Al)As double quantum well as functions of the geometric parameters of the heterostructure are investigated. The variational method is applied within the framework of the parabolic band and effective mass approximations, in order to obtain the 1s-like exciton energy spectrum. The outcome for the related optical coefficients shows a quenched and redshifted light absorption as a result of the increment in the inner barrier and right-hand well widths, with the possibility of an enhancement of the excitonic contribution to the relative change in the refractive index. © 2012 Elsevier B.V.


Miranda G.L.,Fisica Teorica y Aplicada | Mora-Ramos M.E.,Autonomous University of the State of Morelos | Duque C.A.,University of Antioquia
Journal of Luminescence | Year: 2012

The dependencies of the binding energies of the lowest four 1s-like exciton states in GaAs-(Ga,Al)As coupled double quantum wells (CDQW) on the geometric parameters of the system are theoretically studied. A variational approach, together with the parabolic band and effective mass approximations, were considered in order to perform the numerical calculations. It is shown that in the case of a symmetric system there is a degeneracy between the heavy-hole even and odd states and this degeneracy can be removed by the presence of a sufficiently narrow middle barrier. In contrast to this fact, the electron even and odd states are never degenerated. It is detected that, if the system is asymmetric, there will appear binding energies anticrossings between the heavy-hole states at the point of the asymmetric → symmetric QW transition. © 2012 Elsevier B.V. All rights reserved.


Miranda G.L.,Fisica Teorica y Aplicada | Miranda G.L.,University of Antioquia | Mora-Ramos M.E.,Fisica Teorica y Aplicada | Mora-Ramos M.E.,University of Antioquia | And 2 more authors.
Physica E: Low-Dimensional Systems and Nanostructures | Year: 2013

In this work the variational method is applied within the framework of the parabolic band and effective mass approximations, in order to study the 1s-like exciton energy spectrum in the GaAs-Ga 1-xAlxAs asymmetric coupled double quantum well configuration. The obtained states are then used to calculate the coefficient of nonlinear optical rectification associated to the transitions between the excitonic levels. It is shown that different exciton interstate transitions can lead to comparable optical rectification responses. With few exceptions, the increase of the system dimensions implies the appearance of a redshift in the resonant peak positions as well as the fall of their amplitudes. © 2013 Elsevier B.V.


Restrepo R.L.,Fisica Teorica y Aplicada | Restrepo R.L.,University of Antioquia | Miranda G.L.,Fisica Teorica y Aplicada | Miranda G.L.,University of Antioquia | Duque C.A.,University of Antioquia
Journal of Materials Science | Year: 2010

Within the framework of the effective mass and parabolic band approximations and using a variational procedure, a detailed theoretical study of the combined effects of hydrostatic pressure and in-growth direction applied electric field on the electronic states and binding energy of a donor impurity in a GaAs-(Ga,Al)As coupled double quantum well-wires is presented. The particular situation of W-shaped confining potential profile is analyzed. The results obtained show that the energy for the first confined electron states as well as the impurity binding energy bear strong dependences with the hydrostatic pressure, the strength of the applied electric field, and the shape of the confining potential barriers. In the case of the electron states, it is observed that their energies are increasing (decreasing) functions of the potential-shape-related λ-parameter (hydrostatic pressure). It is also found that, in the high hydrostatic pressure regime (25 kbar in this work), the binding energy of a donor impurity decreases with the pressure and the effects of hydrostatic pressure on the potential barriers are predominant over the effects of hydrostatic pressure on the GaAs static dielectric constant. It is shown that the binding energy can increase or decrease depending on the combined effects of the applied electric field and the dimensions of the transversal section of the coupled quantum well wires. © 2010 Springer Science+Business Media, LLC.


Miranda G.L.,Fisica Teorica y Aplicada | Miranda G.L.,University of Antioquia | Restrepo R.L.,Fisica Teorica y Aplicada | Restrepo R.L.,University of Antioquia | Duque C.A.,University of Antioquia
Superlattices and Microstructures | Year: 2011

The combined effects of an in-growth direction applied electric field and hydrostatic pressure on the exciton binding energy and photoluminescence energy transitions are reported in this work for triple vertically coupled quantum dots. The calculations have been carried out within the effective mass approximation, and using a variational procedure. The results show that the exciton binding energy and the photoluminescence energy transitions are functions of external probes like the hydrostatic pressure and the applied electric field. © 2010 Elsevier Ltd. All rights reserved.


Duque C.M.,University of Antioquia | Restrepo R.L.,Fisica Teorica y Aplicada | Duque C.A.,University of Antioquia
Superlattices and Microstructures | Year: 2012

In the present work we report the effects of a geometrical confinement and tilted applied electric field on the electronic energy levels in a semiconducting quantum disk. Calculations are performed in the effective mass approximation and using a variational method. The results can be summarized as follows: (1) due to the infinite confinement along the all directions of the heterostructure, the variational calculation with two parameters for tilted applied electric field can be treated with two independent each other variational parameters; (2) the magnitude of the energy shift is an increasing function of the applied electric field; (3) the effects of the applied electric field are magnified as the dimensions of the heterostructure (height and radius) grow; and finally (4) for large enough applied electric field the energy shift is a linear function of the applied electric field. © 2012 Elsevier Ltd. All rights reserved.

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