Polarization properties of excitonic qubits in single self-assembled quantum dots

Tonin, Catherine; Hostein, Richard; Voliotis, Valia; Grousson, R.; Lemaı̂tre, A.; Martinez, A.

doi:10.1103/physrevb.85.155303

Cited by 67 publications

(86 citation statements)

References 32 publications

(69 reference statements)

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“…(ii) providing an efficient channel for spin decoherence [5][6][7][8][9][10] , (iii) creating a polarization anisotropy of light emission which is important for quantum information schemes [11][12][13][14][15] , and (iv) giving an additional efficient mechanism for optical initialisation of hole spin qubit 16,17 . The origin of this mixing has fascinated physicists and chemists ever since low-dimensional semiconductor nanostructures such as 2D quantum wells, 1D quantum wires, and 0D QDs have been made [11][12][13]19 , yet, the controlling mechanisms are rather vague.…”

Section: Introductionmentioning

confidence: 99%

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: Introductionmentioning

confidence: 99%

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

2015

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“…Within the constant strain field approximation, the phase difference between longitudinal and transverse polarizations is constant and equals π/2, therefore the direction of the polarization ellipse major axis is parallel to the structure elongation direction. Small differences between those two directions have been observed in the experiment [26] but this effect is beyond the scope of the current paper as it is attributed to strain field anisotropy [28]. In the present case, the χ parameter for the emission from a single exciton state β is simply χ (β) = atan[|d…”

Section: The Modelmentioning

confidence: 96%

“…The structure morphology is most clearly manifested in the optical emission via its impact on the polarization properties of luminescence [10,26]. The light hole admixture corresponds to an additional interband transition dipole which interferes with the heavy hole transition dipole leading to an overall elliptical polarization of the emitted radiation.…”

Section: The Modelmentioning

confidence: 99%

Electronic and optical properties of non-uniformly shaped InAs/InP quantum dashes

Kaczmarkiewicz

Machnikowski

2012

Semicond. Sci. Technol.

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Abstract. We theoretically study the optical properties and the electronic structure of highly elongated InAs/InP quantum dots (quantum dashes) and show how carrier trapping due to geometrical fluctuations of the confining potential affects the excitonic spectrum of the system. We focus on the study of the optical properties of a single exciton confined in the structure. The dependence of the absorption and emission intensities on the geometrical properties (size and position) of the trapping centre within the quantum dash is analysed and the dependence of the degree of linear polarization on these geometrical parameters is studied in detail. The role of Coulomb correlations for the optical properties of these structures is clarified. Electronic and optical properties of non-uniformly shaped InAs/InP quantum dashes 2

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“…For the more detailed analysis of the eect of the band--mixing on anisotropy of neutral exciton see [14]. It may be expected that the mixing is more pronounced in the annealed structures as the In/As atom intermixing during the RTA procedure releases strain in the dot and decreases the splitting between the light-hole and heavy--hole bands in the dot.…”

Section: Discussionmentioning

confidence: 99%

“…The polarisation axis of the 3X diers from that of the neutral exciton and depends on the deviation of the excitonic polarization axis from the [110] direction. In our opinion this must result from the mixing between the heavy holes and light holes in the QDs valence band [14].…”

Section: Discussionmentioning

confidence: 99%

The Fine Structure of a Triexciton in Single InAs/GaAs Quantum Dots

et al. 2012

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Results of experimental study of multiexcitonic emission related to the p-shell of single self-assembled InAs/ GaAs quantum dots are presented. Optical properties of a rst emission line to appear from the p-shell of a strongly excited quantum dots are investigated using low-temperature polarization-sensitive micro-photoluminescence measurements. The emission line is attributed to the recombination of a complex of three electrons and holes conned in a dot (neutral triexciton), 3X. It is found that the emission consists of two linearly polarized components and the ne structure splitting is larger than the respective splitting of a neutral exciton. The optical anisotropy of the 3X emission is related to the anisotropy of the quantum dot localizing potential. The axis of the 3X optical anisotropy changes from dot to dot covering broad range within ±50 degrees with respect to the axis dened by the optical anisotropy of a neutral exciton (X). Possible origin of the deviation is discussed.

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Polarization properties of excitonic qubits in single self-assembled quantum dots

Cited by 67 publications

References 32 publications

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

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

Electronic and optical properties of non-uniformly shaped InAs/InP quantum dashes

The Fine Structure of a Triexciton in Single InAs/GaAs Quantum Dots

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