Optical orientation and alignment of excitons in self-assembled<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi mathvariant="normal">Cd</mml:mi><mml:mi mathvariant="normal">Se</mml:mi><mml:mo>∕</mml:mo><mml:mi mathvariant="normal">Zn</mml:mi><mml:mi mathvariant="normal">Se</mml:mi></mml:mrow></mml:math>quantum dots: The role of excited states

Kusrayev, Yu. G.; Koudinov, A. V.; Zakharchenya, B. P.; Lee, S.; Furdyna, J. K.; Dobrowolska, M.

doi:10.1103/physrevb.72.155301

Cited by 43 publications

(45 citation statements)

References 26 publications

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“…The successive spin relaxation associated with phonon-mediated relaxation was observed in CdSe and CdTe QDs. 8,31 To explain the NCP, however, another spin flip-flop process described below and optical orientation of the doped electrons are needed.…”

Section: Resultsmentioning

confidence: 99%

Spin dephasing of doped electrons in charge-tunable InP quantum dots: Hanle-effect measurements

et al. 2006

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The spin dephasing relaxation in single-electron-doped InP quantum dots was studied by means of Hanle measurements. When an InP quantum dot is doped with one electron on average, a narrow Lorentzian dip with half-width of 4.6 mT appeared and was superposed on two Lorentzians with half-widths of 1.54 and 128 mT in the Hanle curve. The half-widths 1.54 T, 128 mT, and 4.6 mT are ascribed to spin-dephasing relaxation of holes, electron-hole pairs, and doped electrons consistuting negative trions, respectively. The corresponding spin coherence time of the doped electrons at 5 K is 1.7 ns, which is determined by the frozen fluctuation of nuclear spins in the quantum dots. With increase of temperature, the spin-dephasing rate of the doped electrons increases.

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Section: Resultsmentioning

confidence: 99%

Spin dephasing of doped electrons in charge-tunable InP quantum dots: Hanle-effect measurements

et al. 2006

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“…For the case of neutral excitons in QDs, a negligible c has been predicted at zero external magnetic field ͑B ext ͒ due to strong anisotropic electron ͑e͒-hole ͑h͒ exchange interaction. [3][4][5][6][7] Conversely, for the case of charged excitons, the anisotropic e-h exchange interaction is suppressed 5,8 and an essential c is expected and has been confirmed in experiments on individual In͑Ga͒As/GaAs QDs. Up to now, a very low c were recorded at B ext = 0 for the neutral exciton in experiments with QD ensembles 6,9 or individual QDs.…”

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confidence: 96%

“…[3][4][5][6][7] Conversely, for the case of charged excitons, the anisotropic e-h exchange interaction is suppressed 5,8 and an essential c is expected and has been confirmed in experiments on individual In͑Ga͒As/GaAs QDs. Up to now, a very low c were recorded at B ext = 0 for the neutral exciton in experiments with QD ensembles 6,9 or individual QDs. 3,8,[10][11][12] In the present report, a high degree ͑ c Ϸ 60%͒ of spin polarization is achieved for the neutral exciton at B ext =0 in individual InAs QDs, studied by micro-photoluminescence ͑ -PL͒.…”

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confidence: 96%

“…20 Hence c ͑proportional to the projection of the exciton pseudospin onto the z axis, ͉S z ex ͉͒ is predicted to be negligible. 4,6,7 However, as stated above, an external magnetic field of sufficient strength ͉B ext ͉ B g ex Ͼប ex ͑ B Ϸ 58 eV/ T is the Bohr magneton and g ex is the neutral exciton g factor͒ applied in Faraday geometry ͑B ext ʈ z͒ "restores" the polarization of the neutral exciton because of decoupling of the ͉+1͘ and ͉−1͘ states. 6,7 At increasing ͉B ext ͉, the ͉+1͘ and ͉−1͘ states are separated in energy by ⌬E = ͕͉͑B ext ͉ B g ex ͒ 2 + ͑ប ex ͒ 2 ͖ 1/2 , 21 which gives rise to a nonvanishing value of c .…”

mentioning

confidence: 99%

“…4,6,7 However, as stated above, an external magnetic field of sufficient strength ͉B ext ͉ B g ex Ͼប ex ͑ B Ϸ 58 eV/ T is the Bohr magneton and g ex is the neutral exciton g factor͒ applied in Faraday geometry ͑B ext ʈ z͒ "restores" the polarization of the neutral exciton because of decoupling of the ͉+1͘ and ͉−1͘ states. 6,7 At increasing ͉B ext ͉, the ͉+1͘ and ͉−1͘ states are separated in energy by ⌬E = ͕͉͑B ext ͉ B g ex ͒ 2 + ͑ប ex ͒ 2 ͖ 1/2 , 21 which gives rise to a nonvanishing value of c . In the vector model, an application of B ext initiates the precession of the exciton pseudospin around the total magnetic field B ⌺ = B ext + ex leading to a nonzero value of ͉S z ex ͉ and hence of c .…”

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confidence: 99%

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Spin polarization of the neutral exciton in a single InAs quantum dot at zero magnetic field

2009

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A high degree of spin polarization for the neutral exciton in individual quantum dots, at zero external magnetic field, is monitored. While a high polarization degree is commonly observed for the charged exciton, a negligible polarization has been predicted for the neutral exciton. The exceptionally high polarization (andgt;60%) observed here is explained in terms of a dynamical nuclear polarization field, stabilizing the electron spin. Such polarization of the quantum dot nuclei, in case of the neutral exciton, is possible due to unequal capture time of electrons and holes.Original Publication:Evgenii Moskalenko, L A Larsson and Per-Olof Holtz, Spin polarization of the neutral exciton in a single InAs quantum dot at zero magnetic field, 2009, PHYSICAL REVIEW B, (80), 19, 193413.http://dx.doi.org/10.1103/PhysRevB.80.193413Copyright: American Physical Societyhttp://www.aps.org

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Light controlled spin properties and radiative coupling of CdSe based quantum dots

Schmidt

Worschech

Scheibner

et al. 2007

Phys. Status Solidi (c)

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The authors have studied the photoluminescence of large and small ensembles of CdSe based quantum dots (QDs) in magnetic fields for different polarizations and powers of the exciting laser light. By means of polarization spectroscopy the g factors and spin lifetimes were determined for semimagnetic CdMnSe QDs with nominal Mn contents of 0%, 1% and 2%. Also the corresponding exciton lifetimes were analyzed. A sign reversal of the QD exciton g factor was identified comparing the polarization of QD luminescence with 0% and 2% Mn. For small excitation powers QDs with 1% Mn have a vanishing small value of g. Interestingly, by ramping up the excitation power of the exciting laser the exciton g factor increases by up to a factor of 30. Different heating mechanism were identified by characteristic power dependencies. For low excitation powers indirect heating of the spin systems occurs whereas above a critical power direct heating due to photoexcited carriers dominates. It is also demonstrated that in CdMnSe QDs the circular polarization of the luminescence can be inverted solely controlled by the laser power. Applying mesa techniques, collective radiance of QDs is demonstrated. For that purpose the radiative lifetimes of QDs with such a density that there are many dots within an area proportional to the square of the optical wavelength were studied for different numbers of QDs removed from that area. A comparison of photoluminescence decay times obtained for non-resonant and quasi-resonant excitation conditions and different mesa sizes is given. Radiative coupling of QDs takes place at least on the order of 150 nm. This length is comparable to the dimensions of lithographically well definable nanostructures and may therefore provide a mechanism to couple discrete quantum objects on a large scale.

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Optical orientation and alignment of excitons in self-assembledCdSe∕ZnSequantum dots: The role of excited states

Cited by 43 publications

References 26 publications

Spin dephasing of doped electrons in charge-tunable InP quantum dots: Hanle-effect measurements

Spin dephasing of doped electrons in charge-tunable InP quantum dots: Hanle-effect measurements

Spin polarization of the neutral exciton in a single InAs quantum dot at zero magnetic field

Light controlled spin properties and radiative coupling of CdSe based quantum dots

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