Observation and explanation of strong electrically tunable exciton<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>g</mml:mi></mml:mrow></mml:math>factors in composition engineered In(Ga)As quantum dots

Jovanov, V.; Eissfeller, T.; Kapfinger, Stephan; Clark, E. C.; Klotz, F.; Bichler, Max; Keizer, JG Joris; Koenraad, PM Paul; Abstreiter, G.; Finley, J. J.

doi:10.1103/physrevb.83.161303

Cited by 37 publications

(40 citation statements)

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“…Efforts have been made to achieve g-tensor manipulation using external electric fields in InGaAs QDs [9][10][11]. Here we report the first observation of strain-induced tuning of the g factor of an exciton confined to an InGaAs QD.…”

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Strain-inducedg-factor tuning in single InGaAs/GaAs quantum dots

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Strain-inducedg-factor tuning in single InGaAs/GaAs quantum dots

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“…The g e in a QD can be tuned via electric field. 35 Therefore, adding electrodes to NFDE QD structures with g e ≈ 0 would allow coherent rotation with an access to an arbitrary part of the electron spin Bloch sphere by switching the value of the electric field. 12,36 The advantage of this approach is that a large number of QD spin qubits can be controlled independently by multiple electrodes on the same semiconductor chip.…”

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confidence: 99%

Vanishing electrongfactor and long-lived nuclear spin polarization in weakly strained nanohole-filled GaAs/AlGaAs quantum dots

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GaAs/AlGaAs quantum dots grown by in situ droplet etching and nanohole infilling offer a combination of strong charge confinement, optical efficiency, and spatial symmetry required for polarization entanglement and spin-photon interface. Here we study spin properties of such dots. We find nearly vanishing electron g-factor (g e < 0.05), providing a route for electrically driven spin control schemes. Optical manipulation of the nuclear spin environment is demonstrated with nuclear spin polarization up to 60% achieved. NMR spectroscopy reveals the structure of two types of quantum dots and yields the small magnitude of residual strain ε b < 0.02% which nevertheless leads to long nuclear spin lifetimes exceeding 1000 s. The stability of the nuclear spin environment is advantageous for applications in quantum information processing.Central spin in semiconductor quantum dots is a prime candidate for applications in quantum information technologies. 1,2 It is relatively isolated from the solid state effects and at the same time is accessible for coherent manipulation and can be interfaced optically. The coherence in this system is mainly limited by the hyperfine coupling with the nuclear spin bath. 3,4 Single spin qubit manipulation in these structures, therefore, demands an auxiliary control over nuclear spin environment. Such control can be realized by maximizing polarization of 10 4 − 10 5 nuclei in a single quantum dot, 5-7 enabling the formation of well-defined nuclear spin states and in effect reducing the influence of the nuclear field fluctuations. 8,9 Central spin manipulation in semiconductor quantum dot (QD) system using resonant ultrafast optical pulses 10,11 has been demonstrated but scalability in such schemes is challenging. An alternative approach is to induce controlled spin rotation by manipulating the coupling to the external magnetic field. 12 This can be achieved by electrical modulation of the g-factor. However, such scheme critically depends on the ability to change the sign of g, thus requiring quantum dots with close to zero electron or hole g-factor. 13,14 Self-assembled InGaAs/GaAs QD has been the primary system of choice for spin studies over the last two decades, as quantum confinement in monolayer-fluctuation GaAs/AlGaAs dots is too weak. Only recently the potential of droplet epitaxial (DE) grown GaAs QDs has been identified. [15][16][17] In particular nanohole-filled droplet epitaxial (NFDE) dots formed by in situ etching and nanohole infilling 18 provide confinement and excellent optical efficiency, while on the other hand exhibiting high symmetry not achievable previously in self-assembled dots. 19 Such unique com-1 arXiv:1507.06553v1 [cond-mat.mes-hall]

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“…Experimental efforts have been made to characterize the g factors (i.e., components of the g tensor) of excitons [21][22][23][24][25][26], and of individual electron and holes [27][28][29][30][31][32][33][34][35][36] confined in quantum dots. Also, electric control over g factors has been shown [25,29,33,[35][36][37]; in particular, it was found that the hole g factor is much more sensitive to an electric field than the electron g factor.…”

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“…Also, electric control over g factors has been shown [25,29,33,[35][36][37]; in particular, it was found that the hole g factor is much more sensitive to an electric field than the electron g factor. As quantum confinement and strain affect the g tensor, it is generally found that the inhomogeneous distribution of quantum dots leads to different g factors and electric-field sensitivities for each individually measured quantum dot.…”

Section: Introductionmentioning

confidence: 99%

“…As quantum confinement and strain affect the g tensor, it is generally found that the inhomogeneous distribution of quantum dots leads to different g factors and electric-field sensitivities for each individually measured quantum dot. Although there are numerous reports of electron or hole g-factor measurements on individual quantum dots, there are only limited systematic reports on the size dependence of the g factors [22][23][24][25]. Moreover, these only involve the exciton g factor in a particular direction, and therefore they do not reveal the size dependence of the separate electron and hole g tensors and their anisotropies.…”

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confidence: 99%

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Anisotropy of electron and holegtensors of quantum dots: An intuitive picture based on spin-correlated orbital currents

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Koenraad, P. M. (2016). Anisotropy of electron and hole g tensors of quantum dots: An intuitive picture based on spin-correlated orbital currents. Physical Review B, 93(3), [035311]. DOI: 10.1103/PhysRevB.93.035311 General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. Using single spins in semiconductor quantum dots as qubits requires full control over the spin state. As the g tensor provides the coupling in a Hamiltonian between a spin and an external magnetic field, a deeper understanding of the g tensor underlies magnetic-field control of the spin. The g tensor is affected by the presence of spin-correlated orbital currents, of which the spatial structure has been recently clarified. Here we extend that framework to investigate the influence of the shape of quantum dots on the anisotropy of the electron g tensor. We find that the spin-correlated orbital currents form a simple current loop perpendicular to the magnetic moment's orientation. The current loop is therefore directly sensitive to the shape of the nanostructure: for cylindrical quantum dots, the electron g-tensor anisotropy is mainly governed by the aspect ratio of the dots. Through a systematic experimental study of the size dependence of the separate electron and hole g tensors of InAs/InP quantum dots, we have validated this picture. Moreover, we find that through size engineering it is possible to independently change the sign of the in-plane and growth direction electron g factors. The hole g tensor is found to be strongly anisotropic and very sensitive to the radius and elongation. The comparable importance of itinerant and localized currents to the hole g tensor complicates the analysis relative to the electron g tensor.

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Observation and explanation of strong electrically tunable excitongfactors in composition engineered In(Ga)As quantum dots

Cited by 37 publications

References 28 publications

Strain-inducedg-factor tuning in single InGaAs/GaAs quantum dots

Strain-inducedg-factor tuning in single InGaAs/GaAs quantum dots

Vanishing electrongfactor and long-lived nuclear spin polarization in weakly strained nanohole-filled GaAs/AlGaAs quantum dots

Anisotropy of electron and holegtensors of quantum dots: An intuitive picture based on spin-correlated orbital currents

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