Exciton Spin Dynamics in Semiconductor Quantum Dots

Marie, X.; Urbaszek, B.; Krebs, O.; Amand, T.

doi:10.1007/978-3-319-65436-2_4

Cited by 1 publication

(1 citation statement)

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“…The degrees of circular and linear polarization (DCP and DLP, respectively) are useful quantitative tools for characterizing the EFS of semiconductor materials and are central to this work; − we define them in the usual convention as DCP = ( I σ+ – I σ– )/( I σ+ + I σ– ), whatever the circular polarization of the excitation, where I σ+ ( I σ– ) is the intensity of σ + (σ – ) circularly polarized component of the emission and DLP = ( I // – I ⊥ )/( I // + I ⊥ ) , with I // and I ⊥ denoting the intensity of the emission analyzed in a direction parallel or perpendicular to the linearly polarized excitation. In nanoparticles, the application of a strong magnetic field induces a Zeeman splitting in the exciton states which manifests itself as a contrast between σ + and σ – emission, under σ + (σ – ) excitation …”

Section: Results and Discussionmentioning

confidence: 99%

Fine Structure and Spin Dynamics of Linearly Polarized Indirect Excitons in Two-Dimensional CdSe/CdTe Colloidal Heterostructures

et al. 2019

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Heterostructured two-dimensional (2D) colloidal nanoplatelets are a class of material that have attracted great interest for optoelectronic applications due to their high photoluminescence yield, atomically tunable thickness and ultralow lasing thresholds. Of particular interest are laterally heterostructured core-crown nanoplatelets with a type-II band alignment, where the in-plane spatial separation of carriers leads to indirect (or charge transfer) excitons with long lifetimes and bright, highly Stokes shifted emission. Despite this, little is known about the nature of the lowest energy exciton states responsible for emission in these materials. Here using polarization-controlled, steadystate and time-resolved photoluminescence measurements, at temperatures down to 1.6 K and magnetic fields up to 30 T, we study the exciton fine structure and spin dynamics of archetypal type-II CdSe/CdTe core-crown nanoplatelets. Complemented by theoretical modelling and zero-field quantum beat measurements we find the brightexciton fine structure consists of two linearly polarized states with a fine structure splitting  50 μeV and an indirect exciton Landé g-factor of 0.7. In addition, we show the exciton spin lifetime to be in the microsecond range with an unusual B -3 magnetic field dependence. The discovery of linearly polarized exciton states and emission highlights the potential for use of such materials in display and imaging applications without polarization filters. Furthermore, the small exciton fine structure splitting and a long spin lifetime are fundamental advantages when envisaging CdSe/CdTe nanoplatelets as elementary bricks for the next generation of quantum devices, particularly given their ease of fabrication.

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