Role of magnetic fluctuations in the luminescence line width of small systems

Brazis, R.; Kossut, J.

doi:10.1016/s0038-1098(02)00064-9

Cited by 31 publications

(19 citation statements)

References 35 publications

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“…As can be seen, the linewidth of this line is of about 4 meV, which is more than an order of magnitude broader than the ~0.1 meV linewidth observed typically for excitons confined to non-magnetic CdTe QDs [32]. This strong broadening of spectral lines is a signature of the formation of magnetic polarons in QDs [30] and is associated with magnetic moment fluctuations within a single QD. The width of the line is related to the binding energy of the EMP [30].…”

mentioning

confidence: 66%

“…This strong broadening of spectral lines is a signature of the formation of magnetic polarons in QDs [30] and is associated with magnetic moment fluctuations within a single QD. The width of the line is related to the binding energy of the EMP [30]. In order to estimate the polaron binding energy we use a simple thermodynamic model, where the emission linewidth, w, should vary as w= (2ε p k B T) 1/2 [30], where ε p is the polaron binding energy, T is the temperature and k B is the Boltzman constant.…”

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confidence: 96%

“…Apart from enhancing the effects of external magnetic field observed for large QD ensemble [14,15,25] and single QDs [25,28,29], the spin interaction between localized Mn ions and localized electron-hole pairs influences also the zero-field behavior of magnetic QDs. One of the most striking is the broadening of a single magnetic dot emission line [28,30,31].…”

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confidence: 99%

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Optical studies of zero-field magnetization of CdMnTe quantum dots: Influence of average size and composition of quantum dots

Gurung

Maćkowski

Jackson

et al. 2004

Journal of Applied Physics

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We show that through the resonant optical excitation of spin-polarized excitons into CdMnTe magnetic quantum dots, we can induce a macroscopic magnetization of the Mn impurities. We observe very broad (4 meV linewidth) emission lines of single dots, which are consistent with the formation of strongly confined exciton magnetic polarons. Therefore we attribute the optically induced magnetization of the magnetic dots results to the formation of spin-polarized exciton magnetic polarons. We find that the photo-induced magnetization of magnetic polarons is weaker for larger dots which emit at lower energies within the QD distribution. We also show that the photo-induced magnetization is stronger for quantum dots with lower Mn concentration, which we ascribe to weaker Mn-Mn interaction between the nearest neighbors within the dots. Due to particular stability of the exciton magnetic polarons in QDs, where the localization of the electrons and holes is comparable to the magnetic exchange interaction, this optically induced spin alignment persists to temperatures as high as 160 K.

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confidence: 66%

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confidence: 96%

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Optical studies of zero-field magnetization of CdMnTe quantum dots: Influence of average size and composition of quantum dots

Gurung

Maćkowski

Jackson

et al. 2004

Journal of Applied Physics

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“…Data reported in literature on the luminescence line FWHM dependence on magnetic field are controversial: a FWHM narrowing [19,20] as well as the FWHM increase [15,21] are calculated and observed. Our experimental results indicate that the FWHM value shows a tendency to decrease in magnetic field (Fig.…”

Section: Luminescence Line Analysismentioning

confidence: 98%

“…Data on the excitonic linewidth dependence on magnetic field are very scarce [15,19,20]. We took an attempt to evaluate more precisely the compositiondisorder-induced part in FWHM value in magnetic field by introducing the dE g /dx = f (B) value [5].…”

Section: Luminescence Line Analysismentioning

confidence: 99%

Luminescence of Cd_0.7Mn_0.3Te crystals in magnetic field: Linewidth, Landau quantization, and carrier effective mass

Barauskaitė¹,

Brazis²,

Ivanov³

et al. 2009

Lithuanian J. Phys.

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Cd0.7Mn0.3Te crystal photoluminescence is studied in magnetic field up to 7 T in Voigt geometry at 1.6-1.7 K temperature. The range of magnetic field where the approximation of effective band gap narrowing by the s, p − d exchange-interactioninduced term correctly describes experimental results is discussed. Luminescence linewidth (FWHM) broadening due to composition disorder and magnetization fluctuations is evaluated. Functional dependence on magnetic field of magnetic part in broadening, the FWHM(B)magn., is determined. From the patterns of Landau quantization in luminescence spectra the carrier effective mass value m * e = 0.104 is calculated and its increase in magnetic field is obtained. Contribution of nonparabolicity and band coupling effects is evaluated in the observed carrier effective mass growth effect.

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Tuning the optical and magnetic properties of II–VI quantum dots by post‐growth rapid thermal annealing

Gurung

Maćkowski

Jackson

et al. 2004

Physica Status Solidi (b)

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We show that both the optical and magnetic properties of CdTe-based quantum dots (QDs) can be tuned by post-growth annealing. With increasing of annealing temperature, the photoluminescence of CdTe and CdMnTe QDs shifts towards high energies. At the same time, we observe a narrowing of the QD ensemble emission linewidth due to the improved homogeneity of the QD ensemble. We find that for annealed CdTe QDs the exciton diamagnetic shift is about two times larger that for the as-grown ones, suggesting an increase of the average dot size upon annealing. In the case of CdMnTe QDs the emission lines of individual quantum dots narrow significantly from 3 meV down to 0.25 meV showing that effect of spin fluctuations is much reduced probably due to an increase of the average dot size.1 Introduction Post-growth annealing has been widely used to change the properties of semiconductor quantum structures [1][2][3]. In particular, it has been shown that for quantum wells both the emission energy and the distribution of magnetic impurities can be modified [1,2]. The latter can lead to substantial changes of the magneto-optical properties of magnetically doped quantum well structures. In the case of Stranski-Krastanov grown III-V semiconductor quantum dots (QDs) which form on top of a twodimensional wetting layer, annealing increases the size of the QDs as well as changes their chemical composition [3]. In contrast, the epitaxial growth of II-VI QDs may occur without the formation of the wetting layer [4], so that annealing will almost certainly affect the strain distribution in and around the QDs. Additionally, since II-VI QDs are usually smaller (a few nanometers in a diameter), one could expect they will react more strongly to annealing than III-V QDs. Finally, for diluted magnetic semiconductor QDs where magnetic ions, such as Mn are incorporated into CdTe QDs [5], annealing might also tune the magnetic characteristics of such QDs.In this work we present the results of photoluminescence (PL) measured for CdMnTe and CdTe QDs subjected to rapid thermal annealing. We find that upon annealing the average size of the QDs increases and the homogeneity of the ensemble improves. In the case of CdMnTe QDs the increase of the dot size leads to a dramatic narrowing of the single dot emission linewidth (from ~3meV down to ~0.2meV). We ascribe this effect to the reduction of magnetic moment fluctuations within individual magnetic QDs.

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Role of magnetic fluctuations in the luminescence line width of small systems

Cited by 31 publications

References 35 publications

Optical studies of zero-field magnetization of CdMnTe quantum dots: Influence of average size and composition of quantum dots

Optical studies of zero-field magnetization of CdMnTe quantum dots: Influence of average size and composition of quantum dots

Luminescence of Cd_0.7Mn_0.3Te crystals in magnetic field: Linewidth, Landau quantization, and carrier effective mass

Tuning the optical and magnetic properties of II–VI quantum dots by post‐growth rapid thermal annealing

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Role of magnetic fluctuations in the luminescence line width of small systems

Cited by 31 publications

References 35 publications

Optical studies of zero-field magnetization of CdMnTe quantum dots: Influence of average size and composition of quantum dots

Optical studies of zero-field magnetization of CdMnTe quantum dots: Influence of average size and composition of quantum dots

Luminescence of Cd0.7Mn0.3Te crystals in magnetic field: Linewidth, Landau quantization, and carrier effective mass

Tuning the optical and magnetic properties of II–VI quantum dots by post‐growth rapid thermal annealing

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Luminescence of Cd_0.7Mn_0.3Te crystals in magnetic field: Linewidth, Landau quantization, and carrier effective mass