Raman Coherence Beats from Entangled Polarization Eigenstates in InAs Quantum Dots

Lenihan, A.S.; Dutt, Meenakshi; Steel, Duncan G.; Ghosh, Siddhartha Sankar; Bhattacharya, P.

doi:10.1103/physrevlett.88.223601

Cited by 104 publications

(72 citation statements)

References 31 publications

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“…Model calculations within the framework of eight-band k·p theory and the configuration interaction method were performed. Different sources for the fine-structure splitting are discussed, and piezoelectricity is pinpointed as the only effect reproducing the observed trend.The exchange interaction of electron-hole pairs (excitons) in semiconductor quantum dots (QDs) has been subject of a lively debate in recent years [1,2,3,4,5,6,7,8]. In such strongly confined systems it is supposed to be enhanced with respect to the bulk case due to the close proximity of electrons and holes.…”

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confidence: 99%

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Size-Dependent Fine-Structure Splitting in Self-OrganizedInAs/GaAsQuantum Dots

et al. 2005

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A systematic variation of the exciton fine-structure splitting with quantum dot size in single InAs/GaAs quantum dots grown by metal-organic chemical vapor deposition is observed. The splitting increases from -80 to as much as 520 µeV with quantum dot size. A change of sign is reported for small quantum dots. Model calculations within the framework of eight-band k·p theory and the configuration interaction method were performed. Different sources for the fine-structure splitting are discussed, and piezoelectricity is pinpointed as the only effect reproducing the observed trend.The exchange interaction of electron-hole pairs (excitons) in semiconductor quantum dots (QDs) has been subject of a lively debate in recent years [1,2,3,4,5,6,7,8]. In such strongly confined systems it is supposed to be enhanced with respect to the bulk case due to the close proximity of electrons and holes. However, the influence of the exact geometry of the confining potential on the exchange interaction still needs to be clarified. A detailed understanding of the resulting exciton fine structure in quantum dots is of fundamental interest and of largest importance for potential applications of QDs in single-photon emitters and entangled two-photon sources for quantum cryptography [9].The total angular momentum M of heavy-hole excitons (X) in QDs is composed of the electron spin (s = ± 1 2 ) and the heavy hole angular momentum (j = ± 3 2 ), consequently producing four degenerate exciton states frequently denoted as dark (M = ±2) and bright (M = ±1) states indicating whether they couple to the photon field or not. Independent of the given confinement symmetry electron-hole exchange interaction causes a dark-bright splitting. Furthermore it mixes the dark states lifting their degeneracy and forming a dark doublet (|2 ±|−2 ). Likewise, additional lowering of the confinement symmetry to C 2v or lower mixes the bright states producing a nondegenerate bright doublet (|1 ± | − 1 ).While emission lines involving pure states are circularly polarized, the mixed states usually produce lines showing linear polarization along the [110] and [110] crystal directions, respectively (Fig. 1). The two bright states are thus directly observable as linearly polarized transitions in luminescence experiments. The energetic difference between these lines is called exciton fine-structure splitting (FSS).The biexciton (XX) ground state is not split by the exchange interaction, since the net spin of the involved electrons and holes is 0. However, the XX to X decay involves two allowed transitions with the final states being the bright states of the X. Therefore, the FSS is reproduced (yet inverted) in the XX to X decay (Fig. 1).Recently reported experimental values of the FSS in * Email: seguin@sol.physik.tu-berlin.de

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confidence: 99%

“…The exchange interaction of electron-hole pairs (excitons) in semiconductor quantum dots (QDs) has been subject of a lively debate in recent years [1,2,3,4,5,6,7,8]. In such strongly confined systems it is supposed to be enhanced with respect to the bulk case due to the close proximity of electrons and holes.…”

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confidence: 99%

Size-Dependent Fine-Structure Splitting in Self-OrganizedInAs/GaAsQuantum Dots

et al. 2005

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“…As shown by experiments 6,18 and theory 19 , the ground state of neutral excitons in the QDs is characterized by two linearly polarized eigenstates, due to an anisotropic electron-hole exchange interaction. Under conditions of spin injection, this will lead to circular polarization quantum beats, that are quickly damped in ensemble measurements 20,21 , resulting in unpolarized PL in continuous-wave experiments as presented here. Therefore, the observed PL polarization must arise from the QDs with strongly reduced exchange interaction so that the circularly polarized ground states are recovered.…”

Section: Fig 2 Ple Spectra (Solid Black Lines) and The Pl Polarizatmentioning

confidence: 99%

Spin injection in lateral InAs quantum dot structures by optical orientation spectroscopy

et al. 2009

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Abstract. Optical spin injection is studied in novel laterally arranged self-assembled InAs/GaAs quantum dot structures, by using optical orientation measurements in combination with tuneable laser spectroscopy. It is shown that spins of uncorrelated free carriers are better conserved during the spin injection than the spins of correlated electrons and holes in an exciton. This is attributed to efficient spin relaxation promoted by the electron-hole exchange interaction of the excitons. Our finding suggests that separate carrier injection, such as that employed in electrical spin injection devices, can be advantageous for spin conserving injection. It is also found that spin injection efficiency decreases for free carriers with high momentum, due to acceleration of spin relaxation processes.

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“…Other energy levels might be accessed using the polarization of the different hole states of the semiconductor, similar to what was been done for quantum dots formed from interface fluctuations of thin GaAs/AlGaAs QW [50,60]. This could only be achieved using normal incidence geometry with multiple layer of SAQD to enhance the absorbance [61,62]. Intrasubband transitions (energy levels in the conduction band) could provide other combinations of energy levels that could be accessed.…”

Section: Suggested Experiments For Observing Coherence Effects In Saqdmentioning

confidence: 99%

Quantum coherence in semiconductor nanostructures for improved lasers and detectors.

Chow¹,

Lyo²,

Cederberg³

et al. 2006

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The potential for implementing quantum coherence in semiconductor self-assembled quantum dots has been investigated theoretically and experimentally. Theoretical modeling suggests that coherent dynamics should be possible in self-assembled quantum dots. Our experimental efforts have optimized InGaAs and InAs self-assembled quantum dots on GaAs for demonstrating coherent phenomena. Optical investigations have indicated the appropriate geometries for observing quantum coherence and the type of experiments for observing quantum coherence have been outlined. The optical investigation targeted electromagnetically induced transparency (EIT) in order to demonstrate an all optical delay line. 5 CONTENTS

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Raman Coherence Beats from Entangled Polarization Eigenstates in InAs Quantum Dots

Cited by 104 publications

References 31 publications

Size-Dependent Fine-Structure Splitting in Self-OrganizedInAs/GaAsQuantum Dots

Size-Dependent Fine-Structure Splitting in Self-OrganizedInAs/GaAsQuantum Dots

Spin injection in lateral InAs quantum dot structures by optical orientation spectroscopy

Quantum coherence in semiconductor nanostructures for improved lasers and detectors.

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