| 1. |
- Dupertuis, M A, et al.
(author)
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Symmetries and the Polarized Optical Spectra of Exciton Complexes in Quantum Dots
- 2011
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In: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 107:12, s. 127403-
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Journal article (peer-reviewed)abstract
- A systematic and simple theoretical approach is proposed to analyze true degeneracies and polarized decay patterns of exciton complexes in semiconductor quantum dots. The results provide reliable spectral signatures for efficient symmetry characterization, and predict original features for low C(2 nu) and high C(3 nu) symmetries. Excellent agreement with single quantum dot spectroscopy of real pyramidal InGaAs/AlGaAs quantum dots grown along [111] is demonstrated. The high sensitivity of biexciton quantum states to exact high symmetry can be turned into an efficient uninvasive postgrowth selection procedure for quantum entanglement applications.
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| 2. |
- Karlsson, Fredrik, 1974-, et al.
(author)
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Electroluminescence and photoluminescence excitation study of asymmetric coupled GaAs/AlxGa1-xAs V-groove quantum wires
- 2004
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In: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 70:4
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Journal article (peer-reviewed)abstract
- We have studied systems of asymmetric coupled GaAs V-groove quantum wires p-i-n diodes, in which the electrons and holes are injected into different wires. Despite the use of a 7 nm thick AlGaAs tunnel barrier, and although we demonstrate that holes tunnel more slowly than electrons, we observe a very efficient and fast tunneling between the quantum wires (QWR's). We attribute this to the achievement of a resonance between hole levels in the two QWR's. Photoluminescence excitation experiments are compared with accurate calculations of the excitonic absorption yielding a level of carrier transfer of nearly 100%. Temperature-dependent electroluminescence exhibits clear effects of tunneling up to room temperature but cannot distinguish separate electron/hole tunneling from exciton tunneling.
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| 3. |
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| 4. |
- Karlsson, Fredrik, et al.
(author)
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Fine structure of exciton complexes in high-symmetry quantum dots: Effects of symmetry breaking and symmetry elevation
- 2010
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In: PHYSICAL REVIEW B. - : American Physical Society. - 1098-0121. ; 81:16, s. 161307-
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Journal article (peer-reviewed)abstract
- Quantum dots (QDs) of high symmetry (e.g., C-3 nu) have degenerate bright exciton states, unlike QDs of C-2 nu symmetry, making them intrinsically suitable for the generation of entangled photon pairs. Deviations from C-3 nu symmetry are detected in real QDs by polarization-resolved photoluminescence spectroscopy in side-view geometry of InGaAs/AlGaAs dots formed in tetrahedral pyramids. The theoretical analysis reveals both an additional symmetry plane and weak symmetry breaking, as well as the interplay with electron-hole and hole-hole exchange interactions manifested by the excitonic fine structure.
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| 5. |
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| 6. |
- Karlsson, Fredrik, 1974-, et al.
(author)
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Fractional-dimensional excitonic absorption theory applied to V-groove quantum wires
- 2004
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In: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 70:15
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Journal article (peer-reviewed)abstract
- A fractional-dimensional approach is applied to a realistic V-groove quantum wire in order to calculate the excitonic absorption spectrum. An excellent agreement is obtained with much more computationally demanding models as well as with experimental photoluminescence excitation data. However, comparison with a full excitonic calculation reveals situations were the concept of fractional dimensions to some extent fails.
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| 7. |
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| 8. |
- Karlsson, K Fredrik, et al.
(author)
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Spectral signatures of high-symmetry quantum dots and effects of symmetry breaking
- 2015
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In: New Journal of Physics. - : Institute of Physics Publishing (IOPP). - 1367-2630. ; 17:10
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Journal article (peer-reviewed)abstract
- High symmetry epitaxial quantum dots (QDs) with three or more symmetry planes provide a very promising route for the generation of entangled photons for quantum information applications. The great challenge to fabricate nanoscopic high symmetry QDs is further complicated by the lack of structural characterization techniques able to resolve small symmetry breaking. In this work, we present an approach for identifying and analyzing the signatures of symmetry breaking in the optical spectra of QDs. Exciton complexes in InGaAs/AlGaAs QDs grown along the [111]B crystalline axis in inverted tetrahedral pyramids are studied by polarization resolved photoluminescence spectroscopy combined with lattice temperature dependence, excitation power dependence and temporal photon correlation measurements. By combining such a systematic experimental approach with a simple theoretical approach based on a point-group symmetry analysis of the polarized emission patterns of each exciton complex, we demonstrate that it is possible to achieve a strict and coherent identification of all the observable spectral patterns of numerous exciton complexes and a quantitative determination of the fine structure splittings of their quantum states. This analysis is found to be particularly powerful for selecting QDs with the highest degree of symmetry ( C 3 v and ##IMG## [http://ej.iop.org/images/1367-2630/17/10/103017/njp519062ieqn1.gif] $D_3h$ ) for potential applications of these QDs as polarization entangled photon sources. We exhibit the optical spectra when evolving towards asymmetrical QDs, and show the higher sensitivity of certain exciton complexes to symmetry breaking.
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| 9. |
- Karlsson, K Fredrik, et al.
(author)
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Symmetry Elevation and Symmetry Breaking : Keys to Describe and Explain Excitonic Complexes in Semiconductor Quantum Dots
- 2011
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In: AIP Conference Proceedings. - : AIP. - 0094-243X.
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Conference paper (peer-reviewed)abstract
- The results of a group theoretical analysis of the excitonic fine structure are presented and compared with spectroscopic data on single quantum dots. The spectral features reveal the signatures of a symmetry higher than the crystal symmetry (C 3v ). A consistent picture of the fine structure patterns for various exciton complexes is obtained with group theory and the concepts of symmetry elevation and symmetry breaking.
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| 10. |
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