Type-I and Type-II Confinement in Quantum Dots: Excitonic Fine Structure

Křápek, Vlastimil; Klenovský, Petr; Šikola, Tomáš

doi:10.12693/aphyspola.129.a-66

Cited by 4 publications

(4 citation statements)

References 18 publications

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“…We further note that considerably smaller FSS for type II corroborates with the results of Refs. [81,82,84] for (In,Ga)As/Ga(As,Sb)/GaAs QDs and, in turn, confirms that to be a rather general property of dots which are type-II in real space. The correlation is obtained in our CI calculations through admixing of excited single-particle states [69].…”

Section: γ-Excitonssupporting

confidence: 65%

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Electronic states of (InGa)(AsSb)/GaAs/GaP quantum dots

2019

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Detailed theoretical studies of the electronic structure of (InGa)(AsSb)/GaAs/GaP quantum dots are presented. This system is unique since it exhibits concurrently direct and indirect transitions both in real and momentum space and is attractive for applications in quantum information technology, showing advantages as compared to the widely studied (In,Ga)As/GaAs dots. We proceed from the inspection of the confinement potentials for k = 0 and k = 0 conduction and k = 0 valence bands, through the formulation of k · p calculations for k-indirect transitions, up to the excitonic structure of Γ-transitions. Throughout this process we compare the results obtained for dots on both GaP and GaAs substrates, enabling us to make a direct comparison to the (In,Ga)As/GaAs quantum dot system. We also discuss the realization of quantum gates.

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Section: γ-Excitonssupporting

confidence: 65%

“…We now proceed with the fine structure of X 0 . That is caused in (In,Ga)As/GaAs QDs [63,81,82] by the effects of isotropic and anisotropic exchange interaction, which is the case also for the present system. The former causes the energy separation of bright and dark X 0 (∆E bd ) while the latter results in FSS of X 0 .…”

Section: γ-Excitonssupporting

confidence: 62%

Electronic states of (InGa)(AsSb)/GaAs/GaP quantum dots

2019

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“…Namely, those are (i) the exchange Coulomb interaction between ground state electron and hole wavefunction (marked as '2 × 2' in figure 3), (ii) the multipole expansion of exchange interaction [75] (marked as '2 × 2 multipole' in figure 3), and (iii) the effect of Coulomb correlation [71,79] (marked as '12 × 12' in figure 3). Clearly, the dominant contribution to both FSS and BD in CdSe/ZnS QDs comes from the multipole expansion of the exchange interaction, similarly as in references [75,80] for III-V QDs. We further note, that the dominant contribution comes from the dipole-dipole term of that expansion for CdSe QDs.…”

Section: Figurementioning

confidence: 71%

Interplay between multipole expansion of exchange interaction and Coulomb correlation of exciton in colloidal II–VI quantum dots

et al. 2022

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We study the effect of Coulomb correlation on the emission properties of the ground state exciton in zincblende CdSe/ZnS core-shell and in wurtzite ZnO quantum dots. We validate our theory model by comparing results of computed exciton energies of CdSe/ZnS quantum dots to photoluminescence and scanning near-field optical microscopy measurements. We use that to estimate the diameter of the quantum dots using a simple model based on infinitely deep quantum well and compare the results with the statistics of the atomic force microscopy scans of CdSe/ZnS dots, obtaining excellent agreement. Thereafter, we compute the energy fine structure of exciton, finding striking difference between properties of zincblende CdSe/ZnS and wurtzite ZnO dots. While in the former the fine structure is dominated by the dipole terms of the multipole expansion of the exchange interaction, in the latter system that is mostly influenced by Coulomb correlation. Furthermore, the correlation sizeably influences also the exciton binding energy and emission radiative rate in~ZnO dots.

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“…We computed the fine structure employing three levels of approximation in CI, i.e., (i) without considering the effect of correlation and with monopole-monopole term of the exchange interaction only, (ii) with correlation and monopole-monopole term of exchange, and (iii) without correlation but with assuming the monopolemonopole, monopole-dipole, and dipole-dipole terms of the exchange interaction what we call multipole expan-sion. [54,64] The results for FSS of X 0 are given in Fig. 3 (a) by full curves along with experimental data from Fig.…”

Section: Theorymentioning

confidence: 99%

Excitonic fine structure of epitaxial Cd(Se,Te) on ZnTe type-II quantum dots

Klenovský,

Baranowski,

Wojnar

2021

Preprint

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The structure of the ground state exciton of Cd(Se,Te) quantum dots embedded in ZnTe matrix is studied experimentally using photoluminescence spectroscopy and theoretically using k • p and configuration interaction methods. The experiments reveal a considerable reduction of fine-structure splitting energy of the exciton with increase of Se content in the dots. That effect is interpreted by theoretical calculations to originate due to the transition from spatially direct (type-I) to indirect (type-II) transition between electrons and holes in the dot induced by increase of Se. The theory results match those of the experiment very well. The theory identifies that the main mechanism causing elevated fine-structure energy in particular in type-I dots is due to the multipole expansion of the exchange interaction. Moreover, the theory reveals that for Se contents in the dot > 0.3, there exist also a confinement related to transition between type I and type II and which exhibits extraordinary properties, such as almost purely light hole character of exciton and toroidal shape of hole states which might be utilized for realization of the Aharonov-Bohm effect.

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Type-I and Type-II Confinement in Quantum Dots: Excitonic Fine Structure

Cited by 4 publications

References 18 publications

Electronic states of (InGa)(AsSb)/GaAs/GaP quantum dots

Electronic states of (InGa)(AsSb)/GaAs/GaP quantum dots

Interplay between multipole expansion of exchange interaction and Coulomb correlation of exciton in colloidal II–VI quantum dots

Excitonic fine structure of epitaxial Cd(Se,Te) on ZnTe type-II quantum dots

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