Near-field magnetoabsorption of quantum dots

Abstract

We investigate the effect of an external magnetic field of variable orientation and magnitude ͑up to 20 T͒ on the linear near-field optical absorption spectra of single and coupled III-V semiconductor quantum dots. We focus on the spatial as well as on the magnetic confinement, varying the dimensions of the quantum dots and the magnetic field. We show that the ground-state exciton binding energy can be manipulated utilizing the spatial and magnetic confinement. The effect of the magnetic field on the absorption spectra, increasing the near-field illumination spot, is also investigated. The zero-magnetic-field "structural" symmetry can be destroyed varying the magnetic field orientation and this affects the near-field spectra. The asymmetry induced ͑except for specific orientations along symmetry axes͒ by the magnetic field can be revealed in the near-field but not in the far-field spectra. We predict that near-field magnetoabsorption experiments, of realistic spatial resolution, will be in the position to bring to light the quantum dot symmetry. This exceptional symmetryresolving power of the near-field magnetoabsorption is lost in the far field. The influence of the Coulomb interactions on the absorption spectra is also discussed. Finally, we show that certain modifications of the magnetoexcitonic structure can be uncovered using a realistically acute near-field probe of Ϸ20 nm.

The effect of the size of self‐assembled individual quantum dots on their PL spectra

“…The details of the theoretical steps for the calculation of the excitonic eigenfunctions have already been presented in Ref. [2]. In Fig.…”

“…For the conduction-band and valence-band offsets we have used ΔV CB = 224 meV and ΔV V B = 180 meV, respectively. We calculate the single-particle eigenstates of electrons and holes within the effective mass and envelope function approximations [2]. The confining potential is zero inside the wetting layer and SAQD, and ΔV CB (or ΔV V B ) inside the barrier.…”

“…γ is a small damping constant that accounts for the coupling with the environment and in the relaxation time approximation is related to the dephasing time as τ =h γ . The excitonic eigenfunction Ψ λ (r, r) is expanded in terms of the single-particle states with coefficients C λ [2,3]. Within this framework it is of interest to investigate the dependence of the PL characteristics upon the size of the self-assembled quantum dots (SAQDs).…”

Charge and heat current rectification by a double-dot system within the Coulomb blockade regime

“…In the present work we study rectifying properties of a system including a double quantum dot placed between two nonferromagnetic electrodes. Double quantum dots are commonly prepared by applying appropriate electrostatic potential to GaAS/AlGaAs heterostructures or heavy molecules [51][52][53][54][55][56][57][58][59]. The dots may be arranged in series [51][52][53][54][55][56] with hard [51][52][53][54] or soft [55,56] barriers separating them.…”

Magneto-optical absorption in semiconducting spherical quantum dots: Influence of the dot-size, confining potential, and magnetic field

“…Existing research work has devoted to understanding diverse fundamental properties of SQDs related with the exciton dynamics. These include the distribution of electrons and holes, exciton formation, exciton binding energy, exciton absorption, recombination, impact ionization, carrier multiplication, direct and indirect transitions, exciton spin dynamics, optical non-linearity, oscillator strength, and excitonic atoms -to name a few -in the theoretical [6-14, 17, 19, 21-22, 24-28, 30-35] and experimental [15,16,18,20,23,29] works. Theoretical models employed for this purpose involve the tight-binding, effective-mass approximation, variational approach, perturbative scheme, finite-element, pseudopotential, and the Kane's k • p model in the systems of CdS, CdSe, PbTe/CdTe, and InAs/GaAs; and considering the effect of an applied magnetic field [13,17,[19][20][21]34], the temperature dependence [23], the phonon effects [25], the Coulomb impurities [30], and the surface effect [32].…”