Electric-field-induced coherent coupling of the exciton states in a single quantum dot

Bennett, A. J.; Pooley, M. A.; Stevenson, R. M.; Ward, M. B.; Patel, Raj B.; Giroday, A. Boyer de la; Sköld, Niklas; Farrer, I.; Nicoll, C. A.; Ritchie, D. A.; Shields, A. J.

doi:10.1038/nphys1780

Cited by 208 publications

(295 citation statements)

References 27 publications

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“…This formula is expected from the classical "folded down" perturbation approach [1][2][3][4][5][6][7][11][12][13][14]16 . On the other hand, all data points of strained In(Ga)As/GaAs QDs exhibit a denominator ∆ HL that is effectively reduced by δ = 78.6 meV with respect to the class of unstrained GaAs QDs and fall then close to another curve:…”

Section: K · P Analysis Of Atomistic Microscopic Resultsmentioning

confidence: 99%

“…The perturbation potential δV C 2v lowers the QD symmetry to C 2v and hence introduces HH-LH mixing, which modifies the ground hole state HH0 [1][2][3][4][5][6][7][11][12][13][14]16,19,22 ,…”

Section: Discussion Of the Supercoupling Effectmentioning

confidence: 99%

“…The two components of the valence band have diametrically opposed fundamental features (including different Bloch functions, pseudospin, type of optical transition, magnitude of effective masses and deformation potentials), so the extent of their quantum mechanical mixing underlies our fundamental understanding of the duality of a broad range of physical properties associated with hole in low-dimensional nanostructures. Specifically, such HH-LH mixing plays important roles in e.g., QDs 1 , including (i) tuning of the excitonic fine-structure splitting [2][3][4] which controls the fidelity of entangled photon pairs,…”

Section: Introductionmentioning

confidence: 99%

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Supercoupling between heavy-hole and light-hole states in nanostructures

2015

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The heavy-hole (HH) and light-hole (LH) components of the valence states in 3D bulk semiconductors can mix quantum mechanically as the dimensionality is reduced in forming 2D, 1D nanostructures and 0D quantum dots (QDs). This coupling controls the tuning of the excitonic fine structure splitting, provides an efficient channel for the spin coherence, and leads to polarization anisotropy of light emission, central to several quantum information schemes. Current understanding is that the mixing scales with the square of δV HL /∆ HL , where δV HL and ∆ HL are the coupling matrix elements of the crystal potential and the energy separation between the primary HH0 and LH0 states, respectively. We discuss two classes of HH-LH coupling mechanisms.First, coupling factors occurring through the numerator δV HL , referred to as "direct coupling", including the well-known (1) quantum confinement, (2) built-in strain, and (3) shape elongation, as well as three additional direct coupling mechanisms discussed here: (4) the intrinsic C 2v crystal field effect, (5) the local symmetry of the interface, and (6) the alloy disorder. We quantify these 6 direct HH-LH coupling effects by performing atomistic pseudopotential calculations on a range of strained and unstrained QDs of different morphologies. We find that in unstrained self-assembled QDs such as GaAs/AlGaAs effects (1)-(6) contribute 0%, 0%, 0%, 0%, 40%, and 60%, respectively, whereas in strained self-assembled QDs such as InGaAs/GaAs they contribute 0%, 0%, 78%, 0%, 8%, and 14%, respectively, to the direct HH-LH coupling δV HL . These relative contributions to direct HH-LH coupling differ significantly from what was previously believed.Second, we discover an unexpected HH-LH coupling that effectively reduces the denominator ∆ HL by the presence of a dense ladder of intermediate states between the HH0 and LH0 states (analogous to super-exchange in magnetism). Supercoupling amplifies and propagates the HH-LH interaction and is the dominant source of HH-LH mixing in strained nanostructures where ∆ HL is fairly large, so by the direct coupling mechanism alone δV HL /∆ HL would be expected to be rather small. Supercoupling explains a number of outstanding puzzles including the surprising fact that in strained (InAs/GaAs) QDs the mixing is very strong despite the fact that ∆ HL is large, and offers a new way to manipulate HH-LH mixing and hence associated properties in nanostructures.

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Section: K · P Analysis Of Atomistic Microscopic Resultsmentioning

confidence: 99%

Section: Discussion Of the Supercoupling Effectmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Supercoupling between heavy-hole and light-hole states in nanostructures

2015

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“…Second, since it has been established that the FSS is related to the atomistic inplane asymmetry between the [110] and [110] crystallographic directions, it would appear that such an intrinsic quantity would not lend itself to tuning via vertical field. Nevertheless, it was shown experimentally that the FSS can be tuned rather effectively in In(Ga)As/GaAs QDs by applying an electric field along the growth direction 13 . Third, the role of strain is unclear: while electric field control was observed in strain-free monolayer thickness fluctuation GaAs QDs 12,14 , investigations of this effect for other strain-free GaAs QDs grown by multi-step hierarchical self-assembly 20 or droplet epitaxy 21 , have not yet been reported.…”

mentioning

confidence: 99%

“…1a) called "fine structure splitting" (FSS) that must be suppressed below the radiative linewidth (≈ 1 µeV). The FSS is affected by the atomistic symmetry of the QD confining potentials 3-8 and can be manipulated by strain 9,10 , lateral electric fields 11 , vertical electric fields [12][13][14] , magnetic field 15 and strong coherent lasers 16,17 . A number of surprising puzzles surround the tuning of the FSS by a vertical electric field.…”

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Influence of the atomic-scale structure on the exciton fine-structure splitting in InGaAs and GaAs quantum dots in a vertical electric field

et al. 2012

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Semiconductor Self‐Assembled Quantum Dots: Present Status and Future Trends

Petroff

2011

Advanced Materials

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Progress in controlling the size, shape, and composition of quantum dots (QDs) as well as their positioning will be crucial to further advances in the fields of quantum information and device applications. The growth of QDs into lattices using controlled positioning of the QD nucleation centers is a possible method. QD positioning is also much needed for further development of QD microcavities and photonic-crystal based devices that are used for quantum information applications. This article discusses the prospects for progress in these fields that may be realized if a better control over the positioning and self-positioning of quantum dots is achieved.

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Electric-field-induced coherent coupling of the exciton states in a single quantum dot

Cited by 208 publications

References 27 publications

Supercoupling between heavy-hole and light-hole states in nanostructures

Supercoupling between heavy-hole and light-hole states in nanostructures

Influence of the atomic-scale structure on the exciton fine-structure splitting in InGaAs and GaAs quantum dots in a vertical electric field

Semiconductor Self‐Assembled Quantum Dots: Present Status and Future Trends

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