Interaction between excitons determines the non-linear response of nanocrystals

Salvador, Mayrose R.; Nair, P. Sreekumari; Cho, Minhaeng; Scholes, Gregory D.

doi:10.1016/j.chemphys.2007.12.020

Cited by 18 publications

(21 citation statements)

References 114 publications

(143 reference statements)

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“…2, and the coloring emphasizes that the spin of the system does not change after an allowed transition, though the orbital angular momentum (and thus the total angular momentum) may change. If the transition is allowed, m ij is set to +1, and set to zero otherwise [33]. The resulting transition dipole moments between the ground state and the fine structure of the single exciton state and between these states and the biexcitonic fine structure states are collected in Table 1 and shown schematically in Fig.…”

Section: Biexcitonic Fine Structure Statesmentioning

confidence: 99%

Using two-dimensional photon echo spectroscopy to probe the fine structure of the ground state biexciton of CdSe nanocrystals

Wong

Scholes

2011

Journal of Luminescence

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Section: Biexcitonic Fine Structure Statesmentioning

confidence: 99%

Using two-dimensional photon echo spectroscopy to probe the fine structure of the ground state biexciton of CdSe nanocrystals

Wong

Scholes

2011

Journal of Luminescence

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“…[101,103] The progression of QDs to rods is illustrated in Figure 6c-e, based on model calculations described elsewhere. [93,104] Emission polarization change is a good example of a consequence of the fine structure ordering. The photoluminescence anisotropy of spherical QDs is depolarized in the plane normal to the c-axis owing to the circularly polarized selection rules for the F ¼ AE1 exciton recombination (see Table 1).…”

Section: Shape Fine Structure and Polarization Anisotropymentioning

confidence: 99%

Controlling the Optical Properties of Inorganic Nanoparticles

Scholes¹

2008

Adv Funct Materials

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The sophistication with which we can now prepare and characterize inorganic nanoparticles has inspired new areas of research into the fundamental properties and applications of these fascinating nanoscale systems. In this article some of the recent ideas concerning control of their optical properties are examined and explained, focusing on semiconductor nanocrystals. It is known that the optical properties of nanocrystals can be size‐tunable, but it is less obvious how shape matters. To explain how size as well as shape matters, the electronic structure of nanocrystals is sketched in relatively simple terms, leading to an introduction to deeper concepts at the heart of spectroscopy such as the exciton fine structure. The exciton fine structure states, although obscured by inhomogeneous line broadening, dictate selection rules for optical excitation. These viewpoints are compared and contrasted to well‐established principles in molecular spectroscopy that provide inspiration as well as perspective. The control of optical poperties is founded on our ability to prepare good quality colloidal particles. Recent advances in nanocrystal shape control are described. The current status of heterostructures is examined, with an emphasis on charge separation in CdSe–CdTe nanorods.

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“…3, note the semilog intensity scale). Other spatially confined systems such as quantum wires 39 and CdSe quantum dots 40 also exhibit clear signatures of intensity induced dephasing. A substantial ex−ex contribution to the linewidth is consistent with exciton confinement effects leading to enhanced exciton-exciton scattering.…”

Section: A Exciton-exciton Scattering Dynamicsmentioning

confidence: 99%

Pure optical dephasing dynamics in semiconducting single-walled carbon nanotubes

Graham

Zhao

Green

et al. 2011

The Journal of Chemical Physics

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We report a detailed study of ultrafast exciton dephasing processes in semiconducting single-walled carbon nanotubes employing a sample highly enriched in a single tube species, the (6,5) tube. Systematic measurements of femtosecond pump-probe, two-pulse photon echo, and three-pulse photon echo peak shift over a broad range of excitation intensities and lattice temperature (from 4.4 to 292 K) enable us to quantify the timescales of pure optical dephasing (T(2)(*)), along with exciton-exciton and exciton-phonon scattering, environmental effects as well as spectral diffusion. While the exciton dephasing time (T(2)) increases from 205 fs at room temperature to 320 fs at 70 K, we found that further decrease of the lattice temperature leads to a shortening of the T(2) times. This complex temperature dependence was found to arise from an enhanced relaxation of exciton population at lattice temperatures below 80 K. By quantitatively accounting the contribution from the population relaxation, the corresponding pure optical dephasing times increase monotonically from 225 fs at room temperature to 508 fs at 4.4 K. We further found that below 180 K, the pure dephasing rate (1/T(2)(*)) scales linearly with temperature with a slope of 6.7 ± 0.6 μeV/K, which suggests dephasing arising from one-phonon scattering (i.e., acoustic phonons). In view of the large dynamic disorder of the surrounding environment, the origin of the long room temperature pure dephasing time is proposed to result from reduced strength of exciton-phonon coupling by motional narrowing over nuclear fluctuations. This consideration further suggests the occurrence of remarkable initial exciton delocalization and makes nanotubes ideal to study many-body effects in spatially confined systems.

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Interaction between excitons determines the non-linear response of nanocrystals

Cited by 18 publications

References 114 publications

Using two-dimensional photon echo spectroscopy to probe the fine structure of the ground state biexciton of CdSe nanocrystals

Using two-dimensional photon echo spectroscopy to probe the fine structure of the ground state biexciton of CdSe nanocrystals

Controlling the Optical Properties of Inorganic Nanoparticles

Pure optical dephasing dynamics in semiconducting single-walled carbon nanotubes

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