Observation of multicharged excitons and biexcitons in a single InGaAs quantum dot

Finley, Jonathan J.; Fry, P. W.; Ashmore, A.; Lemaı̂tre, A.; Tartakovskii, A. I.; Oulton, Ruth; Mowbray, D. J.; Skolnick, M. S.; Hopkinson, M.; Buckle, Philip Derek; Maksym, P. A.

doi:10.1103/physrevb.63.161305

Cited by 162 publications

(126 citation statements)

References 11 publications

(8 reference statements)

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“…The simplest excitonic complexes with such carriers are the excited negatively charged exciton (X − * ) and the doubly negatively charged exciton (X 2− ) in the fundamental state. The properties of electron-electron interaction can be accessed by studying different recombination channels of an X 2− complex [3][4][5][6] or the photoluminescence excitation (PLE) of negatively charged dots 7 . The values of s-p electron-electron exchange integral reported in previous studies vary from about 4 meV 4 for InAs/GaAs QDs, to nearly 80 meV 7 in the case of CdSe/ZnSe QDs.…”

Section: Introductionmentioning

confidence: 99%

Optical study of electron-electron exchange interaction in CdTe/ZnTe quantum dots

et al. 2013

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We present an experimental study of electron-electron exchange interaction in self-assembled CdTe/ZnTe quantum dots based on the photoluminescence measurements. The character and strength of this interaction are obtained by simultaneous observation of various recombination channels of a doubly negatively charged exciton X 2− , including previously unrecognized emission lines related to the electron-singlet configuration in the final state. A typical value of the electron singlettriplet splitting, which corresponds to the exchange integral of electron-electron interaction, has been determined as 20.4 meV with a spread of 1.4 meV across the wide population of quantum dots. We also evidence an unexpected decrease of energy difference between the singlet and triplet states under a magnetic field in Faraday geometry.

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Section: Introductionmentioning

confidence: 99%

Optical study of electron-electron exchange interaction in CdTe/ZnTe quantum dots

et al. 2013

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“…1. The lines labeled 1X and 2X are identified as one-exciton and biexciton emission, respectively, while the lines labeled C1 and C2 are identified as charged-exciton [23] emission. For all of the correlation measurements to be presented, the "start" counter was tuned to the 2X line, and the "stop" counter was tuned to the 1X line.…”

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confidence: 99%

Polarization-correlated photon pairs from a single quantum dot

et al. 2002

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Polarization correlation in a linear basis, but not entanglement, is observed between the biexciton and single-exciton photons emitted by a single InAs quantum dot in a two-photon cascade. The results are well described quantitatively by a probabilistic model that includes two decay paths for a biexciton through a non-degenerate pair of one-exciton states, with the polarization of the emitted photons depending on the decay path. The results show that spin non-degeneracy due to quantumdot asymmetry is a significant obstacle to the realization of an entangled-photon generation device. [4,5,6], but they can also generate sequences of photons in a radiative cascade [7,8]. In such a cascade, each photon has a unique wavelength, and the photons may also have correlated, or even entangled [9] polarizations.In the two-photon cascade, a biexciton singlet state (two electrons and two holes, 2X) decays to one of two optically active single-exciton states (one electron and one hole, 1X) by emitting one photon, and then to the empty-dot state by emitting a second photon. In theory, the polarization properties of photon pairs emitted through these two decay paths result entirely from properties of the optically-active 1X doublet [10,11,12]. For a symmetric quantum dot, the two 1X states are degenerate, and the two decay paths become "indistinguishable," ideally producing polarization-entangled photons [9]. For an asymmetric quantum dot, the 1X doublet is split through the electron-hole exchange interaction into states that couple to photons having orthogonal linear polarizations [13,14,15]. If this splitting is much larger than the radiative linewidth, then the two paths become "distinguishable," with one decay path producing two horizontally-polarized photons and the other producing two vertically polarized photons, for example. In this case, polarization correlation is expected only in a single, preferred basis. Some additional factors are also important, such as spin flip [16] and decoherence processes [17,18,19] that randomize the intermediate 1X state, and valence-band mixing [20].In this article, we present an experimental study of the polarization correlation properties of photon pairs emitted through biexciton decay in a single InAs quantum dot. While temporal correlations between 1X and 2X photons have previously been seen [21], polarization correlation has not yet been reported, to our knowledge, although a lack of such correlation has been mentioned elsewhere [22]. For our sample, we observe a strong polarization correlation in a linear polarization basis, verifying the theoretical picture described above. However, we do not observe entanglement, suggesting that quantum-dot asymmetry is an obstacle to realizing an entangled photon source.A sample was fabricated containing self-assembled InAs quantum dots [3] grown by molecular-beam epitaxy on a (001) GaAs substrate, capped by 75 nm of GaAs. A high growth temperature increased intermixing between the InAs and surrounding GaAs, shortening the quantum-dot emission wa...

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“…At low temperature, recombination into the singlet state has a noticeably larger line width than recombination into the triplet state, that we interpret as a spin dependence of the relaxation mechanism for the p electron in the X 2− final state. The singlet-triplet splitting is typically 4 meV [2,15,16] (sample A) and 7 meV (sample B). Recent experiments also show an additional fine structure: the triplet is not a single line, but a doublet separated by the electron-hole exchange energy of ≈ 0.2 meV in sample B and ≈ 0.1 meV in sample A [17].…”

Section: The Doubly Charged Exciton X 2−mentioning

confidence: 99%

“…If the energy separation between p x and p y is larger than the exchange energy X ee pxpy , the p x orbital is doubly occupied such that S = 0. In the case of an S = 0 X 3− , the PL consists of a single line between the singlet and triplet states of the X 2− emission [15]. In Fig.…”

Section: The Triply Charged Exciton X 3−mentioning

confidence: 99%

Spin-Dependent Coupling of Charged Quantum Dot Excitons with Continuum States

et al. 2004

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Magnetic field and temperature dependent photoluminescence studies on neutral and charged excitons in individual InAs quantum dots allow us to uncover different mechanisms by which the discrete quantum dot states are coupled to delocalized continuum states in a quantum well (the wetting layer). The behaviour of the neutral and singly charged excitons can be explained taking only discrete quantum dot states into account. For doubly and triply charged excitons we have to consider spin dependent coherent and incoherent interactions between discrete quantum dot states and delocalized wetting layer states.

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Observation of multicharged excitons and biexcitons in a single InGaAs quantum dot

Cited by 162 publications

References 11 publications

Optical study of electron-electron exchange interaction in CdTe/ZnTe quantum dots

Optical study of electron-electron exchange interaction in CdTe/ZnTe quantum dots

Polarization-correlated photon pairs from a single quantum dot

Spin-Dependent Coupling of Charged Quantum Dot Excitons with Continuum States

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