Influence of exciton spin relaxation on the photoluminescence spectra of semimagnetic quantum dots

Kłopotowski, Ł.; Cywiński, Łukasz; Szymura, M.; Voliotis, Valia; Grousson, R.; Wojnar, P.; Fronc, K.; Kazimierczuk, T.; Golnik, A.; Karczewski, G.; Wójtowicz, T.

doi:10.1103/physrevb.87.245316

Cited by 14 publications

(24 citation statements)

References 57 publications

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“…The polarization degree (P = (I + − I − )/(I + + I − ), where I ± are PL intensities in σ ± polarizations) of the X − PL reaches only about 50%. This difference points out that in semimagnetic QDs exciton spin relaxation is faster than spin relaxation of the hole, 26 which controls the polarization behavior of the X − transition.…”

Section: Resultsmentioning

confidence: 92%

“…39 The obtained number of Mn ions remains in a good agreement with a value expected for a QD with an intentional Mn concentration of 0.05. 26 For assessing the nature of the inter-dot coupling, the most important result is that we reproduce the experimental data with γ e = 0 and γ h = 0.07 for the σ − polarization and γ h = 0.09 for the σ + polarization. Thus, we conclude that the observed Zeeman shifts and transition linewidths originate from a small penetration of the hole wave function from the CdTe dot into the Cd 1−x Mn x Te dot.…”

Section: Resultsmentioning

confidence: 99%

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Optical signatures of spin-dependent coupling in semimagnetic quantum dot molecules

et al. 2015

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We present photoluminescence studies of CdTe and Cd1−xMnxTe quantum dots grown in two adjacent layers. We show that when the dots are 8 nm apart, their magnetooptical properties -Zeeman shifts and transition linewidths -are analogous to those of individual CdTe or Cd1−xMnxTe dots. When the dots are grown closer, at a distance of 4 nm, it becomes possible to tune the electron states to resonance and obtain a formation of a molecular state hybridized over the two dots. As a result of the resonant enhancement of the electron-Mn ion exchange interaction, spectroscopic signatures specific to spin-dependent inter-dot coupling appear. Namely, an anomalous increase of the Zeeman shift and a resonant increase in the transition linewidth are observed. A simple model calculation allows us to quantitatively reproduce the experimental results.

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Section: Resultsmentioning

confidence: 92%

Section: Resultsmentioning

confidence: 99%

Optical signatures of spin-dependent coupling in semimagnetic quantum dot molecules

et al. 2015

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“…One should also take into account the Varshni shift when analyzing the temperature variation of hν [3]. Moreover, our calculated E MP values cannot be directly compared to MP signatures seen in those QDs, where recombination time is smaller or comparable to MP formation time [30].…”

Section: Comparison To Experimentsmentioning

confidence: 99%

Multiband Electronic Structure of Magnetic Quantum Dots: Numerical Studies

et al. 2018

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Semiconductor quantum dots (QDs) doped with magnetic impurities have been a focus of continuous research for a couple of decades. A significant effort has been devoted to studies of magnetic polarons (MP) in these nanostructures. These collective states arise through exchange interaction between a carrier confined in a QD and localized spins of the magnetic impurities (typically: Mn). Our theoretical description of various MP properties in self-assembled QDs is discussed. We present a self-consistent, temperature-dependent approach to MPs formed by a valence band hole. The Luttinger-Kohn k ¤ p Hamiltonian is used to account for the important effects of spin-orbit interaction.

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“…Furthermore, as explained previously, the intrinsic (i.e. not related to presence of photo-excited carriers) processes of spin relaxation of Mn 2+ spins are becoming more efficient as the Mn 2+ concentration increases, and in most of samples of dilute magnetic semiconductors the possibility of localized spins simply relaxing in the molecular field generated by spin-polarized photocarriers is a priori possible (in reality one has to take into account competition between this process and the process of fast spin relaxation of carriers in presence of their large spin splitting generated by large number of Mn 2+ ions interacting with each electron and hole [20,49]). For a single Mn 2+ spin interacting with excitons confined in three dimensions, i.e.…”

Section: Introductionmentioning

confidence: 99%

Mechanisms of optical orientation of an individual Mn²⁺ ion spin in a II–VI quantum dot

Smoleński¹,

Cywiński²,

Kossacki³

2018

J. Phys.: Condens. Matter

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We provide a theoretical description of the optical orientation of a single Mn 2+ ion spin under quasi-resonant excitation demonstrated experimentally by Goryca et al. [Phys. Rev. Lett. 103, 087401 (2009)]. We build and analyze a hierarchy of models by starting with the simplest assumptions (transfer of perfectly spin-polarized excitons from Mn-free dot to the other dot containing a single Mn 2+ spin, followed by radiative recombination) and subsequently adding more features, such as spin relaxation of electrons and holes. Particular attention is paid to the role of the influx of the dark excitons and the process of biexciton formation, which are shown to contribute significantly to the orientation process in the quasi-resonant excitation case. Analyzed scenarios show how multiple features of the excitonic complexes in magnetically-doped quantum dots, such as the values of exchange integrals, spin relaxation times, etc., lead to a plethora of optical orientation processes, characterized by distinct dependencies on light polarization and laser intensity, and occurring on distinct timescales. Comparison with experimental data shows that the correct description of the optical orientation mechanism requires taking into account Mn 2+ spin-flip processes occurring not only when the exciton is already in the orbital ground state of the light-emitting dot, but also those that happen during the exciton transfer from high-energy states to the ground state. Inspired by the experimental results on energy relaxation of electrons and holes in nonmagnetic dots, we focus on the process of biexciton creation allowed by mutual spin-flip of an electron and the Mn 2+ spin, and we show that by including it in the model, we obtain good qualitative and quantitative agreement with the experimental data on quasi-resonantly driven Mn 2+ spin orientation.

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Influence of exciton spin relaxation on the photoluminescence spectra of semimagnetic quantum dots

Cited by 14 publications

References 57 publications

Optical signatures of spin-dependent coupling in semimagnetic quantum dot molecules

Optical signatures of spin-dependent coupling in semimagnetic quantum dot molecules

Multiband Electronic Structure of Magnetic Quantum Dots: Numerical Studies

Mechanisms of optical orientation of an individual Mn²⁺ ion spin in a II–VI quantum dot

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Influence of exciton spin relaxation on the photoluminescence spectra of semimagnetic quantum dots

Cited by 14 publications

References 57 publications

Optical signatures of spin-dependent coupling in semimagnetic quantum dot molecules

Optical signatures of spin-dependent coupling in semimagnetic quantum dot molecules

Multiband Electronic Structure of Magnetic Quantum Dots: Numerical Studies

Mechanisms of optical orientation of an individual Mn2+ ion spin in a II–VI quantum dot

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Product

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Mechanisms of optical orientation of an individual Mn²⁺ ion spin in a II–VI quantum dot