Anomalous in-plane magneto-optical anisotropy of self-assembled quantum dots

Kießling, T.; Platonov, A. V.; Astakhov, G. V.; Slobodskyy, T.; Mahapatra, S.; Ossau, W.; Schmidt, G.; Βrunner, Karl; Molenkamp, L. W.

doi:10.1103/physrevb.74.041301

Cited by 13 publications

(12 citation statements)

References 15 publications

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“…The situation is more complicated for the Voigt measurements, as it is neither possible to assign the measured g factors to a specific carrier, nor to establish their sign: it is a priori not clear which of the two linearly polarized Zeeman splittings belongs to which transition. It has been shown for quantum wells [48] and ensembles of quantum dots [49] that the in-plane orientation of the linear polarization axis depends on the relative in-plane orientation of the electron and hole spin. Details of the hole state, such as light-hole intermixing and the nonlinear remote-band coupling of the magnetic field to the hole spin, can lead to the peculiar situation in which the in-plane orientation of the polarization axis depends nontrivially on the in-plane magnetic-field orientation [49].…”

Section: -8mentioning

confidence: 99%

“…It has been shown for quantum wells [48] and ensembles of quantum dots [49] that the in-plane orientation of the linear polarization axis depends on the relative in-plane orientation of the electron and hole spin. Details of the hole state, such as light-hole intermixing and the nonlinear remote-band coupling of the magnetic field to the hole spin, can lead to the peculiar situation in which the in-plane orientation of the polarization axis depends nontrivially on the in-plane magnetic-field orientation [49]. Only by measuring this dependence would it be possible to attribute the Zeeman splittings to a certain carrier.…”

Section: -8mentioning

confidence: 99%

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

et al. 2016

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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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Section: -8mentioning

confidence: 99%

Section: -8mentioning

confidence: 99%

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

et al. 2016

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“…The optical anisotropy of QDs was also studied by applying a magnetic field in the Voigt geometry, which revealed a complex behavior due to shape asymmetry and strain present in self-assembled quantum dots ͑SAQDs͒. [14][15][16][17] In principle, probing different charged excitonic states in QDs could yield different values of the Zeeman splittings if the Coulomb correlations between carriers altered the singleparticle wave function of the strongly confined carriers. Coulomb interactions between carriers confined in QDs are exemplified by the rich optical spectra of multiply charged excitonic complexes demonstrating the role of exchange interactions between electrons or holes.…”

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Coulomb correlations of charged excitons in semiconductor quantum dots

et al. 2009

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The emission pattern of charged excitons in a semiconductor quantum dot ͑QD͒ is composed of a quadruplet of linearly polarized lines when a magnetic field is applied in a Voigt configuration. The orientation of the linear polarization of exciton emission is controlled by the orientation of the magnetic field in QDs with C 3v symmetry while for QDs with C 2v symmetry it is not. We demonstrate that the g factor of holes is very sensitive to the dot shape asymmetry but that of electrons is not. By comparing the effective g factors obtained for the neutral and charged excitons in the same quantum dot, we uncover the role of Coulomb correlations in these excitonic states. We show that the C 3v symmetry of pyramidal QDs makes them ideal candidates for implementing all-optical many-qubits gates based on electron spin as a quantum bit. DOI: 10.1103/PhysRevB.80.165312 PACS number͑s͒: 78.67.Hc, 71.70.Ej, 71.70.Gm, 78.55.Cr Spin degree of freedom of carriers in semiconductor quantum dots ͑QDs͒ could serve as quantum bits to store 1 and process 2,3 information in spin-based devices. Recent experiments demonstrated essential steps toward the implementation of these concepts. Effective initialization of a spin state was achieved for either an electron 4,5 or a hole 6,7 confined to a single quantum dot. Rapid rotation of an electron spin was accomplished by driving coherently the two spin states with short optical pulses by means of stimulated spinflip Raman scattering. 8 The coherent manipulation of a carrier spin 9 in a spin-flip Raman process involves the creation of two energetically different spin states by applying a magnetic field. A key property of an electron ͑or a hole͒ confined to a QD is the effective g factor that measures the Zeeman splitting of the ground state in an applied magnetic field and depends on the orientation of the field with respect to the symmetry axis of the QD. Even though the coherent manipulation of a single quantum dot spin was successively demonstrated, the extension of this scheme to quantum dot arrays seems to be a challenge as QDs must have a narrow distribution of emission energies and obey specific optical selection rules. It is thus necessary to investigate the homogeneity of the Zeeman splittings and the uniformity of the optical selection rules in QD arrays.Zeeman splittings in QDs have been investigated by capacitance spectroscopy, 10 by magnetophotoluminescence 11,12 and by transient nonlinear optical techniques.13 While transport techniques probe the g factors of electronic states, optical techniques probe the Zeeman splittings of excitonic states. The optical anisotropy of QDs was also studied by applying a magnetic field in the Voigt geometry, which revealed a complex behavior due to shape asymmetry and strain present in self-assembled quantum dots ͑SAQDs͒. 14-17In principle, probing different charged excitonic states in QDs could yield different values of the Zeeman splittings if the Coulomb correlations between carriers altered the singleparticle wave function of the strong...

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“…For observation of a second spherical harmonic it is known from the above that the axis of the polarization vector must be fixed to a distinct crystal axis independent of the orientation of the magnetic field vector [24]. This situation is displayed in Fig.…”

Section: Optical Polarization Rotation Induced By In-plane Magnetic Fmentioning

confidence: 97%

“…However, due to the heavy-hole light-hole mixing in the valence bands of QDs, which is certainly present, additional matrix elements arise in the angular momentum operator. They can in principle be taken into account in empirical parameters, when the optical response in modelled quantitatively [24]. To fully take into account the valence band mixing in the framework of the above formalism, clearly additional data is required.…”

Section: Optical Polarization Rotation Induced By In-plane Magnetic Fmentioning

confidence: 99%

Optical studies of structural and magnetic anisotropies in epitaxial CdSe/ZnSe quantum dots

Kießling

Astakhov

Platonov

et al. 2007

Phys. Status Solidi (c)

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We summarize experimental studies on the optical polarization properties of MBE-grown shape-asymmetric self-assembled CdSe/ZnSe quantum dots (QDs). The zero magnetic field fine structure splitting of excitonic transitions in structurally anisotropic QDs gives rise to an effective linear-to-circular and circular-to-linear optical polarization conversion upon resonant excitation of the QD ensemble. The effect is qualitatively modelled in terms of a pseudospin formalism. Furthermore, we show how an in-plane magnetic field leads to a complex rotation behavior of the axis of the optical polarization. Our analysis based on the exciton pseudospin Hamiltonian unambiguously displays that these effects are induced by isotropic and anisotropic contributions to the heavy hole Zeeman term. Likewise we show that the latter mechanism can be used to tune the optical respone of shape-anisotropic QDs such that the optical polarization properties are equal to QDs of perfect D 2d symmetry.

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Anomalous in-plane magneto-optical anisotropy of self-assembled quantum dots

Cited by 13 publications

References 15 publications

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

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

Coulomb correlations of charged excitons in semiconductor quantum dots

Optical studies of structural and magnetic anisotropies in epitaxial CdSe/ZnSe quantum dots

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