The influence of the surrounding semiconducting matrix upon the polarizability of embedded nanoobjects ͑quantum dots͒ has been investigated. The previously proposed hybrid model has been extended to accommodate the influence of embedding. It turns out that excess discrete dipoles having an excess polarizability against a uniform background identical to the dielectric host material build the basis for a modified discrete dipole model, suited to describe the optical response of this system. The individual dipoles are described by means of dielectric embedded oblate ellipsoids as to their static response. An efficient description of the electrostatics of these ellipsoids has been given in terms of explicit functions using cylindrical coordinates and compatible with similar derivations for spherical dielectric objects. The dynamic contribution, responsible for frequency dependence is determined quantum mechanically and added to the embedded bare polarizability. The result of the model for the particular InAs quantum dot GaAs host combination investigated is a slightly decreased internal reflectance as compared to vacuum and an overall strong increment of the absorbance, the structure in the reflectance and of the ellipsometric angles.
The influence of the surrounding semiconducting matrix upon the polarizability of embedded nano-objects (nano-rings) has been investigated using a hybrid discrete/continuum model. It describes embedded systems by excess discrete dipoles with excess polarizability against a uniform background with the host material dielectric constant. The polarizability combines the static polarizability of an ellipsoidal ring with a dynamic quantum mechanical frequency dependent term. The result of the model for the particular nano-ring host combination investigated is an increased internal reflectance and an overall strong increment of the structure in reflectance/ellipsometric angles, displaying clearly the optical Aharonov-Bohm effect.
We consider lowest energy states of electrons confined in asymmetrical circular vertically stacked double InAs/GaAs quantum dot molecule. The energies where computed by using the effective three-dimensional one band Hamiltonian, the energy (non-parabolic) and position dependent electronic effective mass approximation, and the Ben Daniel-Duke boundary conditions with the finite hard wall confinement potential. We demonstrated theoretically a possibility to drive dynamically coupled electronic states (relocate electronic wave functions from one dot to another) by applying external magnetic field.1 Introduction Recent advances in the fabrication of semiconductor nano-scale-objects stimulated much attention to the study of structural, optical, and electronic properties of semiconductor quantum dots (see for example [1]). Especially, during the last decade it has become possible to fabricate realistic semiconductor quantum dots in laboratories. Various experimental results demonstrate that InAs/GaAs quantum dots can have diverse shapes, such as disk, ellipsoid, or conical shapes with a circular top view cross section and a large area-to-height aspect ratio (see for instance [2,3]). Coupled quantum dots allow us to form an artificial molecule. In this molecule we can adjust the inter-dot distance and through that to control coupling between electronic states localized in different dots. The ability to control coherent coupling between double quantum dots may open possibility for designing quantum logic gates (see [4,5] and references therein). The inter-dot distance control is an example of a static approach to the gate's design. Another possibility to control dynamically the coupling lies in application of external fields [6].In this work we demonstrate theoretically an opportunity to drive dynamically electronic states by applying external magnetic field to two vertically coupled InAs/GaAs quantum dots.
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