Linear polarization of the photoluminescence of quantum wells subject to in-plane magnetic fields

Koudinov, A. V.; Averkiev, N. S.; Kusrayev, Yu. G.; Namozov, B. R.; Zakharchenya, B. P.; Wolverson, Daniel; Davies, J.; Wójtowicz, T.; Karczewski, G.; Kossut, J.

doi:10.1103/physrevb.74.195338

Cited by 18 publications

(15 citation statements)

References 28 publications

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“…The first term in the above Hamiltonian will be further called Zeeman part of the LK Hamiltonian because of its similarity to standard Zeeman Hamiltonian. It is well known from studies of quantum wells that this term leads to the additional heavy-hole lighthole mixing 43,44 , however in our case such additional mixing strength is more than order of magnitude weaker than mechanism presented in Eq. 1 The second part depends on the third power of the momentum operators and therefore will be referred to as the cubic term of the LK Hamiltonian.…”

Section: Theoretical Modelmentioning

confidence: 56%

Anisotropy of in-plane holegfactor in CdTe/ZnTe quantum dots

et al. 2016

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Optical studies of a bright exciton provide only limited information about the hole anisotropy in a quantum dot. In this work we present a universal method to study heavy hole anisotropy using a dark exciton in a moderate in-plane magnetic field. By analysis of the linear polarization of the dark exciton photoluminescence we identify both isotropic and anisotropic contributions to the hole g-factor. We employ this method for a number of individual self-assembled CdTe/ZnTe quantum dots, demonstrating a variety of behaviors of in-plane hole g-factor: from almost fully anisotropic to almost isotropic. We conclude that, in general, both contributions play an important role and neither contribution can be neglected.

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Section: Theoretical Modelmentioning

confidence: 56%

Anisotropy of in-plane holegfactor in CdTe/ZnTe quantum dots

et al. 2016

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“…, where -directions, i.e., a reflection of the cubic symmetry of the host lattice). Based on the previous experience, 8,17 we believe that the function Eq. ( 2)…”

Section: Models and Resultsmentioning

confidence: 99%

Angular harmonics of the excitonic polarization conversion effect

Koudinov

2011

Phys. Rev. B

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IntroductionThe term 'polarization conversions' appeared in mid-1990s with regard to the polarization phenomena observed at the conditions of optical pumping of GaAs/(Al,Ga)As layered nanostructures.1,2 In particular, the external magnetic field applied along the growth axis caused the appearance of the circularly polarized component of the photoluminescence (PL) at a linearly polarized optical excitation or, vice versa, appearance of the linearly polarized component of the PL at a circularly polarized excitation. The 'linear-to-linear conversion', i.e., merely the rotation of the plane of polarization of the PL with respect to that of the excitation light, was also observed. 2 Taking a broader view of things, one can consider as 'conversions' all the collection of the exciton-mediated relationships between the three polarization parameters of the excitation light and the three polarization parameters of the PL. With such an interpretation, well-known effects of optical orientation and optical alignment of excitons 3 are particular forms of the conversions.Later on, the conversions effect was reported for quantum dot layers. Models and resultsWe shall calculate optical polarization responses of a layer of uncharged quantum dots where neutral excitons are created by the polarized optical excitation. We consider two-step models of the exciton evolution, and the relaxation is not taken into account. We allow for random orientations of the principal axes of the QDs' lower (ground) state potential (in-plane 'elongations' of QDs, where the inhomogeneous in-plane strain distribution can add to the QD shape effect 15,16 ). Confirmed by various ensemble and single-QD experiments, the directional scatter is a well-established reality for many epitaxial QD systems. We shall describe it by a probability density function, where where capital Θ s refer to the upper, small θ s -to the lower state. Together with the parameters β α , of the angular function Eq.(2) they form the full parameter system of the problem.We searched for all the polarization components of the luminescence for the cases of linearly where i specifies the incoming-, j -the outgoing polarization, ' L stands for the linear polarization degree in the axes rotated by 45° with respect to the vertical direction, coefficients ij C are functions of B but not of ϕ . Table are marked (corr). By this model we have in mind large QDs (each of them contains several exciton levels) being excited by photons whose energy exceed the PL energy only slightly. Second, a fully non-correlated conversion (marked n/corr), i.e., the excited-state potential has arbitrary direction of the in-plane elongation with no relationship to the ground-state elongation. Third, an almost non-correlated conversion (marked n/corr*), i.e., the excited-state potential is elongated parallel to [110] for all the QDs with no relationship to the ground-state elongation. The latter two models can be compared to the case of small QDs as emitting states and the excitons being generated in the wetting ...

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“…9 In practice, however, the transverse g factor of heavy holes in QDs and in QWs is often determined by structural distortions in the plane of the layer. [10][11][12] Possible sources of such distortions are the anisotropy of the localizing potential ͑e.g., shape anisotropy of the QDs͒, fluctuations in local distribution of strain of the atomic bonds ͑uniaxial in-plane deformations͒, or a combination of both these factors. Recent studies have shown that the effect of deformations is probably more pronounced in QDs.…”

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Spin depolarization of holes and lineshape of the Hanle effect in semiconductor nanostructures

et al. 2009

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We report the statistical effect of random in-plane deformations on the magnetic field depolarization of photoluminescence ͑the Hanle effect͒ in quasi-two-dimensional semiconductor nanostructures such as quantum wells or disklike quantum dots. Provided that the optical orientation signal from the sample is due to the nonequilibrium spin polarization of holes, the lineshape of the Hanle effect becomes non-Lorentzian. This results from a scatter of hole g-factor values, which is immanent to the hole ensembles in such systems. Analysis of the lineshape of the Hanle effect holds promise as a tool for distinguishing between X + and X − trion states in nanostructures.In light of the enhanced interest in studying spin phenomena in low-dimensional semiconductor nanostructures such as quantum wells ͑QWs͒ and quantum dots ͑QDs͒, including details of spin structure, it is convenient to employ optical spin orientation measurements. For bulk semiconductor crystals, the optical orientation signal usually arises due to the nonequilibrium spin polarization of the conduction-band or donor-bound electrons. In the case of holes there exists a strong correlation between spin and momentum, so that the nonequilibrium spin polarization of the holes dissipates after a few momentum changing collisions. 1 Such depolarization typically occurs on a subpicosecond time scale, while typical hole lifetimes are of the order of hundreds of picoseconds. As a rule, therefore, on average the nonequilibrium spin polarization is nearly absent in an ensemble of holes, so that the holes do not contribute to the optical orientation signal in continuous-wave ͑cw͒ experiments.The situation is, however, quite different in twodimensional ͑2D͒ quantum nanostructures. In that case the motion of the holes is restricted by the confinement potential, and the energy spectrum of the valence band is thus fundamentally changed as compared to that of the bulk crystal. Typically, the lowest-energy valence-band state in such 2D situations is the heavy-hole subband, while the light-hole subband is split off due to the difference in effective masses and to biaxial strain in the 2D layer. The Kramers sublevels of the heavy hole Ϯ3 / 2 differ by the value of 3 in the angular-momentum projection. This fact restricts the number of random interactions which can mix these sublevels and initiate the spin flip of the hole. Indeed, while for "warm" holes in a QW spin relaxation remains quite efficient, it slows down noticeably for "cold" holes at the bottom of the band. 2 The possibilities for spin relaxation are further restricted in QDs, where the motion of holes is limited in all three dimensions and the energy spectrum is discrete. One should bear in mind that in QDs ͑and in fact also in QWs͒ the excitonic effects, particularly the electron-hole exchange interaction, become strong, and can mask the pure spin properties of holes of interest in this Brief Report. A convenient way to eliminate the influence of the exchange interaction on spin relaxation of holes ͑and thus on opti...

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Linear polarization of the photoluminescence of quantum wells subject to in-plane magnetic fields

Cited by 18 publications

References 28 publications

Anisotropy of in-plane holegfactor in CdTe/ZnTe quantum dots

Anisotropy of in-plane holegfactor in CdTe/ZnTe quantum dots

Angular harmonics of the excitonic polarization conversion effect

Spin depolarization of holes and lineshape of the Hanle effect in semiconductor nanostructures

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