Fast Spin State Initialization in a Singly Charged InAs-GaAs Quantum Dot by Optical Cooling

Xu, Xiaodong; Wu, Yanwen; Sun, Bo; Huang, Qiong; Cheng, Jun; Steel, Duncan G.; Bracker, Allan S.; Gammon, D.; Emary, Clive; Sham, L. J.

doi:10.1103/physrevlett.99.097401

Cited by 277 publications

(282 citation statements)

References 26 publications

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“…Figure 2 shows also the spectra of the same two typical QDs in the Voigt geometry: For QD1 shown in panel (a) the total number of lines we are able to resolve is two for each charged exciton (X + and X − ), and not four as could be expected by analogy with [001] samples. 5,[25][26][27] This is true both in the circular (σ + /σ − ) and the linear basis (π x /π y ). Analysing a quantum dot with lower symmetry allowed us to uncover the true polarization basis and lift the remaining degeneracies.…”

Section: Resultsmentioning

confidence: 99%

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Magnetic field induced valence band mixing in [111] grown semiconductor quantum dots

Durnev¹,

Glazov²,

Ivchenko³

et al. 2013

Phys. Rev. B

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We present a microscopic theory of the magnetic field induced mixing of heavy-hole states ±3/2 in GaAs droplet dots grown on (111)A substrates. The proposed theoretical model takes into account the striking dot shape with trigonal symmetry revealed in atomic force microscopy. Our calculations of the hole states are carried out within the Luttinger Hamiltonian formalism, supplemented with allowance for the triangularity of the confining potential. They are in quantitative agreement with the experimentally observed polarization selection rules, emission line intensities and energy splittings in both longitudinal and transverse magnetic fields for neutral and charged excitons in all measured single dots.

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Section: Resultsmentioning

confidence: 99%

“…5, [25][26][27], where two transition lines are observed in the Faraday, and four well separated transitions in the Voigt geometry. Symmetry arguments, presented in Sec.…”

Section: Introductionmentioning

confidence: 99%

Magnetic field induced valence band mixing in [111] grown semiconductor quantum dots

Durnev¹,

Glazov²,

Ivchenko³

et al. 2013

Phys. Rev. B

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“…The initialization of a single electron spin has been demonstrated under application of a magnetic field in Voigt 44,45 or Faraday 46 geometry and cw excitation. The initialization in the Voigt configuration is three orders of magnitude quicker than in the Faraday configuration, but the fidelity of this latter configuration is greater.…”

Section: Discussionmentioning

confidence: 99%

Hole-spin initialization and relaxation times in InAs/GaAs quantum dots

et al. 2011

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We study, at low temperature and zero magnetic field, the hole-spin dynamics in InAs/GaAs quantum dots. We measure the hole-spin relaxation time at a time scale longer than the dephasing time (about ten nanoseconds), imposed by the hole-nuclear hyperfine coupling. We use a pump-probe configuration and compare two experimental techniques based on differential absorption. The first one works in the time domain, and the second one is a new experimental method, the dark-bright time-scanning spectroscopy (DTS), working in the frequency domain. The measured hole-spin relaxation times, using these two techniques, are very similar, in the order of T h N ≈1 μs. It is mainly imposed by the inhomogeneous hole hyperfine coupling in the hole localization volume. The DTS technique allows us also to measure the hole-spin initialization time τ i . The hole spin is initialized by a periodic train of circularly polarized pulses at 76 MHz; we have observed that τ i decreases as the power density increases, and we have measured a minimum value of τ i ≈100 ns in good agreement with a simple model [seeB. Eble, P. Desfonds, F. Fras, F. Bernardot, C. Testelin, M. Chamarro, A. Miard, and A. Lemaître, Phys. Rev. B 81, 045322 (2010)].

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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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Fast Spin State Initialization in a Singly Charged InAs-GaAs Quantum Dot by Optical Cooling

Cited by 277 publications

References 26 publications

Magnetic field induced valence band mixing in [111] grown semiconductor quantum dots

Magnetic field induced valence band mixing in [111] grown semiconductor quantum dots

Hole-spin initialization and relaxation times in InAs/GaAs quantum dots

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

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