Exciton lifetimes of CdTe nanocrystal quantum dots in high magnetic fields

Blokland, J.H.; Claessen, Victor I.; Wijnen, Frans J. P.; Groeneveld, Esther; Donegá, Celso de Mello; Vanmaekelbergh, Daniël; Meijerink, Andries; Maan, J. C.; Christianen, Peter C. M.

doi:10.1103/physrevb.83.035304

Cited by 33 publications

(58 citation statements)

References 32 publications

(67 reference statements)

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“…17 In QDs ensemble, the symmetry axes are randomly oriented and bright-dark mixing occur. 13,15,25,35 Following commonly used k.p theory, the mixing appears because the off diagonal terms in the Hamiltonian are non-zero when the magnetic field is not strictly parallel to the q-axis. In this case, the only possibility to explain an absence of bright-dark mixing lays in the vanishing of the matrix element which couples the excitonic states.…”

Section: Discussionmentioning

confidence: 99%

“…19,20 Applying an external magnetic field induces a shortening of the long component, which eventually converges towards the bright exciton radiative lifetime. To date these fingerprints have been observed in many colloidal nanostructures: CdSe, 21 CdSe/ZnS, 17,18 CdSe/CdS (dot-in-rod, 13,22 spherical with thin shell 14,16 ), CdSe nanoplatelets, 23,24 spherical CdTe, 25 Lead-halide perovskite. 26,27…”

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confidence: 99%

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Hyperfine Interactions and Slow Spin Dynamics in Quasi-isotropic InP-based Core/Shell Colloidal Nanocrystals

et al. 2019

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Colloidal InP core/sell nanocrystals are taking over CdSe-based nanocrystals, notably in optoelectronic applications. Despite their use in commercial device such as display screens, the optical properties of InP nanocrystals and especially their relation with the exciton fine structure remains poorly understood. In this work, we show that the magneto-optical properties of ensemble InP-based core/shell nanocrystals investigated in strong magnetic fields up to 30 T are strikingly different compared to other colloidal nanostructures. Notably, the mixing of the lowest spin-forbidden dark exciton state with the nearest spin-allowed bright state does not occur, up to the highest magnetic fields applied. This lack of mixing in ensemble of nanocrystals suggests an anisotropy-tolerance of InP nanocrystals. This striking property allowed us to unveil the slow spin dynamics between Zeeman sublevels (up to 400 ns at 15 T). Furthermore, we show that the unexpected magnetic field-induced lengthening of the dark exciton lifetime results from the hyperfine interaction between the spin of the electron in the dark exciton with the nuclear magnetic moments. Our results demonstrate the richness of the spin physics in InP quantum dots and stress the large potential of InP nanostructures for spin-based applications. KEYWORD:colloidal nanostructure, III-V, hyperfine interaction, dark exciton, high magnetic field

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Section: Discussionmentioning

confidence: 99%

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confidence: 99%

Hyperfine Interactions and Slow Spin Dynamics in Quasi-isotropic InP-based Core/Shell Colloidal Nanocrystals

et al. 2019

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“…On the left, we depict the energy levels in a perfectly spherical crystal in the absence of a B-field: two manifolds separated by electronÀhole exchange over a gap Δ 0 . 29 We estimate (see Supporting Information) that the value of Δ 0 (∼0.3 meV) for sample 9 nm is of the order of k B T even at cryogenic temperatures, indicating that all X states are thermally populated. When corrections due to shape anisotropy are also taken into account, the manifolds split (see Figure 3C).…”

Section: Article Dmentioning

confidence: 99%

Quantum Confinement Regimes in CdTe Nanocrystals Probed by Single Dot Spectroscopy: From Strong Confinement to the Bulk Limit

et al. 2015

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Sufficiently large semiconductor nanocrystals are a useful model system to characterize bulk-like excitons, with the electron and hole bound predominantly by Coulomb interaction. We present optical characterization of excitons in individual giant CdTe nanocrystals with diameters up to 25.5 nm at 4.2 K under varying excitation power and magnetic field strength. We determine values for the biexciton binding energy, diamagnetic shift constant, and Landé g-factor, which approach the bulk values with increasing nanocrystal size.

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“…Colloidal NCs have also reach potential applications in the devices exploring the spin degree of freedom. [10][11][12] The effect of an applied magnetic field on the exciton recombination dynamics has been studied for CdSe [13][14][15][16], PbSe [17] and CdTe [18] NCs. The impact is most pronounced at low temperatures, when in equilibrium the dark exciton states are predominantly populated.…”

Section: Introductionmentioning

confidence: 99%

Exciton spin dynamics of colloidal CdTe nanocrystals in magnetic fields

et al. 2014

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The recombination and spin dynamics of excitons in colloidal CdTe nanocrystals (NCs) are studied by time-resolved photoluminescence in high magnetic fields up to 15 T and at cryogenic temperatures. The recombination decay shows a nonexponential temporal behavior, with the longest component corresponding to the dark excitons having 260 ns decay time at zero magnetic field and 4.2 K temperature. This long component shortens to 150 ns at 15 T due to the magnetic-fieldinduced mixing of the bright and dark exciton states. The spin dynamics, assessed through the evolution of the magnetic-field-induced circular polarization degree of the photoluminescence, has a fast component shorter than 1 ns related to the bright excitons and a slow component of 5-10 ns associated with the dark excitons. The latter shortens with increasing magnetic field, which is characteristic for a phonon-assisted spin relaxation mechanism. The relatively low saturation level of the associated magnetic-field-induced circular polarization degree of −30% is explained by a model that suggests the CdTe NCs to constitute an ensemble of prolate and oblate NCs, both having a structural quantization axis. The exciton g-factor of 2.4-2.9 evaluated from fitting the experimental data in the frame of the suggested approach is in good agreement with the expected value for the dark excitons in CdTe NCs.

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Exciton lifetimes of CdTe nanocrystal quantum dots in high magnetic fields

Cited by 33 publications

References 32 publications

Hyperfine Interactions and Slow Spin Dynamics in Quasi-isotropic InP-based Core/Shell Colloidal Nanocrystals

Hyperfine Interactions and Slow Spin Dynamics in Quasi-isotropic InP-based Core/Shell Colloidal Nanocrystals

Quantum Confinement Regimes in CdTe Nanocrystals Probed by Single Dot Spectroscopy: From Strong Confinement to the Bulk Limit

Exciton spin dynamics of colloidal CdTe nanocrystals in magnetic fields

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