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ABSTRACT: Silicene is the counterpart of graphene and its potential applications as a
part of the current electronics, based in silicon, make it a very important
system to study. We perform molecular dynamics simulations and analyze the
structure of a two dimensional array of Si atoms by means of the radial
distribution function, at different temperatures and densities. As a first
approach, the 2D Lennard-Jones potential is used and two sets of parameters are
tested. We find that the radial distribution function does not change with the
parameters and resembles the corresponding to the (111) surface of the FCC
structure. The liquid phase appears at very high temperatures, suggesting a
very stable system in the solid phase.
12/2011;
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ABSTRACT: The self-assembled quantum dot with lens domain has rotational symmetry but it is intrinsically asymmetric when the electron moves perpendicularly to its circular base, {\it i. e.} along the rotational axis. To characterize this asymmetry, an external electric field is applied along the positive or negative direction of the rotational axis. We report the different Stark shifts appearing in the spectra as a function of the field intensity for different lens domains. It is shown that for a flat lens domain the asymmetry effects decrease, but even for very flat lenses they can not be approximated by a cylindrical domain. Finally, some optical properties such as the dielectric constant and electroabsorption are studied. Signatures of the energy spectrum reveal in these quantities. The importance of considering the proper lens domain as long as the magnitude and direction field to tune a specific level transition is stressed.
11/2005;
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ABSTRACT: We present a theoretical approach to study the effects of an ac-field applied to quantum dots with semi-spherical symmetry. Using the Floquet formalism for this periodically driven system, the time-dependent Hamiltonian in the effective mass approximation is solved. We show that the Hilbert space of solutions is separated into orthogonal subspaces with different $z$-component of the angular momentum. We give an explicit analytical representation for electronic states as a function of the intensity and frequency of the electric field. Under the two level approximation, two particular cases are studied: the low- and high-frequency regimes, which result of comparing the ac-field frequency to the characteristic level splitting at zero field. Comment: 3 pages, one figure
07/2005;
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ABSTRACT: The electronic and optical properties of the cleavage InAs(110) surface are studied using a semi-empirical tight-binding method which employs an extended atomic-like basis set. We describe and discuss the electronic character of the surface electronic states and we compare with other theoretical approaches, and with experimental observations. We calculate the surface electronic band structure and the Reflectance Anisotropy Spectrum, which are described and discussed in terms of the surface electronic states and the atomic structure.
Revista Mexicana de Fisica 11/2003; 51:168. · 0.37 Impact Factor
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ABSTRACT: The electronic properties of the cleavage InAs(110) surface are studied using a semi-empirical tight-binding method which employs an extended atomic-like basis set. We calculate the surface electronic band structure which is studied as a function of the structural parameters of the surface. We describe and discuss the electronic character of the surface electronic states and we compare with other theoretical approaches, and with experimental observations. Finally, we discuss which atomic model better resembles the available experimental data.
05/2003;
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ABSTRACT: The electronic and optical properties of the cleavage InAs(110) surface are studied using a semi-empirical tight-binding method which employs an extended atomic-like basis set. We calculate the surface electronic band structure and the Reflectance Anisotropy Spectrum. We describe and discuss the optical properties in terms of the surface electronic states and we compare our results with other theoretical approaches, and with experimental observations. (C) 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
PHYSICA STATUS SOLIDI C: CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 0, NO 8; 01/2003
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ABSTRACT: We study the time evolution of electronic spin in a double quantum dot system (quantum dot molecule, QDM) under strong harmonic fields in the terahertz region. The dynamics of the wavefunction for a single electron includes the spin–orbit (SO) effects of both Rashba and Dresselhaus types and is obtained in terms of Floquet states and the quasienergy spectrum. A low magnetic field applied perpendicular to the plane of the QDM provides additional flexibility. We find that it is possible to control the electronic spin from a given initial state by proper choice of applied fields. The electron can be either dynamical localized or allowed to oscillate between the dots, with or without SO-induced spin flip.
Physica E Low-dimensional Systems and Nanostructures 40(5):1226-1228. · 1.53 Impact Factor
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ABSTRACT: Theoretical results for single-electron states of lens-shaped self-assembled quantum dots under intense harmonic electric fields are presented. We analyze the time evolution of the system utilizing a nonperturbation Floquet state approach. The full lens geometry is taken into account, allowing us to study the interplay between the spatial asymmetry of the confinement and the magnitude, direction, and frequency of the applied field. Dynamical symmetries and localization are revealed in the structure of Hilbert space of functions and the associated quasienergy spectrum. We discuss the role of the different quasienergy sidebands as the parameters of the system change for light incident parallel and perpendicular to the lens axis. We find that the contribution of different drive harmonics is controlled by fine tuning of field intensity. We further show that avoided crossings in the quasienergy spectrum are correlated with the spectral force of the sidebands and dynamical state localization.
Phys. Rev. B. 77(23).
