1
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Golovatenko AA, Kalitukha IV, Dimitriev GS, Sapega VF, Rakhlin MV, Galimov AI, Shubina TV, Shornikova EV, Qiang G, Yakovlev DR, Bayer M, Biermann A, Hoffmann A, Aubert T, Hens Z, Rodina AV. A Comparative Study of the Band-Edge Exciton Fine Structure in Zinc Blende and Wurtzite CdSe Nanocrystals. NANOMATERIALS (BASEL, SWITZERLAND) 2022; 12:4269. [PMID: 36500892 PMCID: PMC9736692 DOI: 10.3390/nano12234269] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Revised: 11/24/2022] [Accepted: 11/27/2022] [Indexed: 06/17/2023]
Abstract
In this paper, we studied the role of the crystal structure in spheroidal CdSe nanocrystals on the band-edge exciton fine structure. Ensembles of zinc blende and wurtzite CdSe nanocrystals are investigated experimentally by two optical techniques: fluorescence line narrowing (FLN) and time-resolved photoluminescence. We argue that the zero-phonon line evaluated by the FLN technique gives the ensemble-averaged energy splitting between the lowest bright and dark exciton states, while the activation energy from the temperature-dependent photoluminescence decay is smaller and corresponds to the energy of an acoustic phonon. The energy splittings between the bright and dark exciton states determined using the FLN technique are found to be the same for zinc blende and wurtzite CdSe nanocrystals. Within the effective mass approximation, we develop a theoretical model considering the following factors: (i) influence of the nanocrystal shape on the bright-dark exciton splitting and the oscillator strength of the bright exciton, and (ii) shape dispersion in the ensemble of the nanocrystals. We show that these two factors result in similar calculated zero-phonon lines in zinc blende and wurtzite CdSe nanocrystals. The account of the nanocrystals shape dispersion allows us to evaluate the linewidth of the zero-phonon line.
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Affiliation(s)
| | - Ina V. Kalitukha
- Ioffe Institute, Russian Academy of Sciences, 194021 St. Petersburg, Russia
| | | | - Victor F. Sapega
- Ioffe Institute, Russian Academy of Sciences, 194021 St. Petersburg, Russia
| | - Maxim V. Rakhlin
- Ioffe Institute, Russian Academy of Sciences, 194021 St. Petersburg, Russia
| | - Aidar I. Galimov
- Ioffe Institute, Russian Academy of Sciences, 194021 St. Petersburg, Russia
| | - Tatiana V. Shubina
- Ioffe Institute, Russian Academy of Sciences, 194021 St. Petersburg, Russia
| | - Elena V. Shornikova
- Experimentelle Physik 2, Technische Universität Dortmund, 44221 Dortmund, Germany
| | - Gang Qiang
- Experimentelle Physik 2, Technische Universität Dortmund, 44221 Dortmund, Germany
| | - Dmitri R. Yakovlev
- Ioffe Institute, Russian Academy of Sciences, 194021 St. Petersburg, Russia
- Experimentelle Physik 2, Technische Universität Dortmund, 44221 Dortmund, Germany
| | - Manfred Bayer
- Experimentelle Physik 2, Technische Universität Dortmund, 44221 Dortmund, Germany
| | - Amelie Biermann
- Institut für Festkörperphysik, Technische Universitat Berlin, 10623 Berlin, Germany
| | - Axel Hoffmann
- Institut für Festkörperphysik, Technische Universitat Berlin, 10623 Berlin, Germany
| | - Tangi Aubert
- Department of Chemistry, Ghent University, 9000 Ghent, Belgium
| | - Zeger Hens
- Department of Chemistry, Ghent University, 9000 Ghent, Belgium
| | - Anna V. Rodina
- Ioffe Institute, Russian Academy of Sciences, 194021 St. Petersburg, Russia
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2
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Fedin I, Goryca M, Liu D, Tretiak S, Klimov VI, Crooker SA. Enhanced Emission from Bright Excitons in Asymmetrically Strained Colloidal CdSe/Cd xZn 1-xSe Quantum Dots. ACS NANO 2021; 15:14444-14452. [PMID: 34473467 DOI: 10.1021/acsnano.1c03864] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Colloidal CdSe quantum dots (QDs) designed with a high degree of asymmetric internal strain have recently been shown to host a number of desirable optical properties including subthermal room-temperature line widths, suppressed spectral diffusion, and high photoluminescence (PL) quantum yields. It remains an open question, however, whether they are well-suited for applications requiring emission of identical single photons. Here we measure the low-temperature PL dynamics and the polarization-resolved fluorescence line narrowing spectra from ensembles of these strained QDs. Our spectroscopy reveals the radiative recombination rates of bright and dark excitons, the relaxation rate between the two, and the energy spectra of the quantized acoustic phonons in the QDs that can contribute to relaxation processes. In comparison to conventional colloidal CdSe/ZnS core/shell QDs, we find that in asymmetrically strained CdSe QDs over six times more light is emitted directly by the bright exciton. These results are therefore encouraging for the prospects of chemically synthesized colloidal QDs as emitters of single indistinguishable photons.
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Affiliation(s)
- Igor Fedin
- Chemistry Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
- Department of Chemistry and Biochemistry, University of Alabama, Tuscaloosa, Alabama 35487, United States
| | - Mateusz Goryca
- National High Magnetic Field Lab, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Dan Liu
- Theory Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Sergei Tretiak
- Theory Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Victor I Klimov
- Chemistry Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Scott A Crooker
- National High Magnetic Field Lab, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
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3
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Qiang G, Golovatenko AA, Shornikova EV, Yakovlev DR, Rodina AV, Zhukov EA, Kalitukha IV, Sapega VF, Kaibyshev VK, Prosnikov MA, Christianen PCM, Onushchenko AA, Bayer M. Polarized emission of CdSe nanocrystals in magnetic field: the role of phonon-assisted recombination of the dark exciton. NANOSCALE 2021; 13:790-800. [PMID: 33351019 DOI: 10.1039/d0nr07117j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The recombination dynamics and spin polarization of excitons in CdSe nanocrystals synthesized in a glass matrix are investigated using polarized photoluminescence in high magnetic fields up to 30 Tesla. The dynamics are accelerated by increasing temperature and magnetic field, confirming the dark exciton nature of low-temperature photoluminescence (PL). The circularly polarized PL in magnetic fields reveals several unusual appearances: (i) a spectral dependence of the polarization degree, (ii) its low saturation value, and (iii) a stronger intensity of the Zeeman component which is higher in energy. The latter feature is the most surprising being in contradiction with the thermal population of the exciton spin sublevels. The same contradiction was previously observed in the ensemble of wet-chemically synthesized CdSe nanocrystals but was not understood. We present a theory which explains all the observed features and shows that the inverted ordering of the circularly polarized PL maxima from the ensemble of nanocrystals is a result of competition between the zero phonon (ZPL) and one optical phonon-assisted (1PL) emission of the dark excitons. The essential aspects of the theoretical model are different polarization properties of the dark exciton emission via ZPL and 1PL recombination channels and the inhomogeneous broadening of the PL spectrum from the ensemble of nanocrystals exceeding the optical phonon energy.
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Affiliation(s)
- Gang Qiang
- Experimentelle Physik 2, Technische Universität Dortmund, 44227 Dortmund, Germany.
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4
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Khosla M, Rao S, Gupta S. Polarons Explain Luminescence Behavior of Colloidal Quantum Dots at Low Temperature. Sci Rep 2018; 8:8385. [PMID: 29849075 PMCID: PMC5976793 DOI: 10.1038/s41598-018-26678-w] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2018] [Accepted: 05/11/2018] [Indexed: 02/03/2023] Open
Abstract
Luminescence properties of colloidal quantum dots have found applications in imaging, displays, light-emitting diodes and lasers, and single photon sources. Despite wide interest, several experimental observations in low-temperature photoluminescence of these quantum dots, such as the short lifetime on the scale of microseconds and a zero-longitudinal optical phonon line in spectrum, both attributed to a dark exciton in literature, remain unexplained by existing models. Here we propose a theoretical model including the effect of solid-state environment on luminescence. The model captures both coherent and incoherent interactions of band-edge exciton with phonon modes. Our model predicts formation of dressed states by coupling of the exciton with a confined acoustic phonon mode, and explains the short lifetime and the presence of the zero-longitudinal optical phonon line in the spectrum. Accounting for the interaction of the exciton with bulk phonon modes, the model also explains the experimentally observed temperature-dependence of the photoluminescence decay dynamics and temperature-dependence of the photoluminescence spectrum.
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Affiliation(s)
- Meenakshi Khosla
- Department of Electrical Engineering, Indian Institute of Technology Kanpur, Kanpur, 208016, UP, India.,Department of Electrical and Computer Engineering, Cornell University, Ithaca, NY, 14850, USA
| | - Sravya Rao
- Department of Electrical Engineering, Indian Institute of Technology Kanpur, Kanpur, 208016, UP, India
| | - Shilpi Gupta
- Department of Electrical Engineering, Indian Institute of Technology Kanpur, Kanpur, 208016, UP, India.
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5
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Granados Del Águila A, Jha B, Pietra F, Groeneveld E, de Mello Donegá C, Maan JC, Vanmaekelbergh D, Christianen PCM. Observation of the full exciton and phonon fine structure in CdSe/CdS dot-in-rod heteronanocrystals. ACS NANO 2014; 8:5921-31. [PMID: 24861569 DOI: 10.1021/nn501026t] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Light emission of semiconductor nanocrystals is a complex process, depending on many factors, among which are the quantum mechanical size confinement of excitons (coupled electron-hole pairs) and the influence of confined phonon modes and the nanocrystal surface. Despite years of research, the nature of nanocrystal emission at low temperatures is still under debate. Here we unravel the different optical recombination pathways of CdSe/CdS dot-in-rod systems that show an unprecedented number of narrow emission lines upon resonant laser excitation. By using self-assembled, vertically aligned rods and application of crystallographically oriented high magnetic fields, the origin of all these peaks is established. We observe a clear signature of an acoustic-phonon assisted transition, separated from the zero-phonon emission and optical-phonon replica, proving that nanocrystal light emission results from an intricate interplay between bright (optically allowed) and dark (optically forbidden) exciton states, coupled to both acoustic and optical phonon modes.
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Affiliation(s)
- Andrés Granados Del Águila
- High Field Magnet Laboratory, Institute for Molecules and Materials, Radboud University Nijmegen , Toernooiveld 7, 6525 ED Nijmegen, The Netherlands
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6
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Mews A, Eychmüller A. Quantum Wells within Quantum Dots, a CdS/HgS Nanoheterostructure with Global and Local Confinement. ACTA ACUST UNITED AC 2014. [DOI: 10.1002/bbpc.199800003] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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7
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Lo SS, Major TA, Petchsang N, Huang L, Kuno MK, Hartland GV. Charge carrier trapping and acoustic phonon modes in single CdTe nanowires. ACS NANO 2012; 6:5274-5282. [PMID: 22559050 DOI: 10.1021/nn3010526] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Semiconductor nanostructures produced by wet chemical synthesis are extremely heterogeneous, which makes single particle techniques a useful way to interrogate their properties. In this paper the ultrafast dynamics of single CdTe nanowires are studied by transient absorption microscopy. The wires have lengths of several micrometers and lateral dimensions on the order of 30 nm. The transient absorption traces show very fast decays, which are assigned to charge carrier trapping into surface defects. The time constants vary for different wires due to differences in the energetics and/or density of surface trap sites. Measurements performed at the band edge compared to the near-IR give slightly different time constants, implying that the dynamics for electron and hole trapping are different. The rate of charge carrier trapping was observed to slow down at high carrier densities, which was attributed to trap-state filling. Modulations due to the fundamental and first overtone of the acoustic breathing mode were also observed in the transient absorption traces. The quality factors for these modes were similar to those measured for metal nanostructures, and indicate a complex interaction with the environment.
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Affiliation(s)
- Shun Shang Lo
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556-5670, USA
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8
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Fernée MJ, Littleton BN, Rubinsztein-Dunlop H. Detection of bright trion states using the fine structure emission of single CdSe/ZnS colloidal quantum dots. ACS NANO 2009; 3:3762-3768. [PMID: 19835398 DOI: 10.1021/nn9010158] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
We report direct observation of the lowest two states of the band-edge exciton fine structure in the photoluminescence from single CdSe/ZnS core/shell nanocrystals at cryogenic temperatures. The temperature dependence of this spectral fingerprint reveals exciton spin relaxation rates as low as 10 micros(-1). The fine structure is also dependent on the nanocrystal charge state facilitating the identification of a bright negatively charged trion state with a quantum yield comparable to that of neutral emission.
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Affiliation(s)
- Mark J Fernée
- Centre for Quantum Computer Technology, School of Physical Sciences, The University of Queensland, Queensland, Australia.
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9
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Oron D, Aharoni A, de Mello Donega C, van Rijssel J, Meijerink A, Banin U. Universal role of discrete acoustic phonons in the low-temperature optical emission of colloidal quantum dots. PHYSICAL REVIEW LETTERS 2009; 102:177402. [PMID: 19518829 DOI: 10.1103/physrevlett.102.177402] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2008] [Indexed: 05/05/2023]
Abstract
Multiple energy scales contribute to the radiative properties of colloidal quantum dots, including magnetic interactions, crystal field splitting, Pauli exclusion, and phonons. Identification of the exact physical mechanism which couples first to the dark ground state of colloidal quantum dots, inducing a significant reduction in the radiative lifetime at low temperatures, has thus been under significant debate. Here we present measurements of this phenomenon on a variety of materials as well as on colloidal heterostructures. These show unambiguously that the dominant mechanism is coupling of the ground state to a confined acoustic phonon, and that this mechanism is universal.
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Affiliation(s)
- Dan Oron
- Department of Physics of Complex Systems, Weizmann Institute of Science, Rehovot, Israel
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10
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Chilla G, Kipp T, Menke T, Heitmann D, Nikolic M, Frömsdorf A, Kornowski A, Förster S, Weller H. Direct observation of confined acoustic phonons in the photoluminescence spectra of a single CdSe-CdS-ZnS core-shell-shell nanocrystal. PHYSICAL REVIEW LETTERS 2008; 100:057403. [PMID: 18352427 DOI: 10.1103/physrevlett.100.057403] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2007] [Indexed: 05/26/2023]
Abstract
We report on the direct observation of confined acoustic phonons in the photoluminescence spectra of single CdSe-CdS-ZnS nanocrystals, whose ligands were exchanged to poly(ethylene oxide) (PEO) before they were embedded in a PEO matrix. Modeling a nanocrystal as an elastic sphere, the confined acoustic modes can be assigned to purely radial vibrations: the breathing mode and its two first radial harmonics. In addition to acoustic modes, we also observe longitudinal optical modes of the core material and, remarkably, also of both shell materials.
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Affiliation(s)
- Gerwin Chilla
- Institut für Angewandte Physik und Zentrum für Mikrostrukturforschung, Universität Hamburg, Jungiusstrasse 11, 20355 Hamburg, Germany
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11
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Huxter VM, Scholes GD. Nonlinear optical approach to multiexciton relaxation dynamics in quantum dots. J Chem Phys 2006; 125:144716. [PMID: 17042640 DOI: 10.1063/1.2354480] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Unlike the majority of molecular systems quantum dots can accommodate multiple excitations, which is a particularly important attribute for potential lasing applications. We demonstrate in this work the concept of using nth order nonlinear spectroscopies in the transient grating configuration as a means of selectively exciting (n-1)/2 excitons in a semiconductor and probing the subsequent relaxation dynamics. We report a direct observation of multiparticle dynamics on ultrashort time scales through comparison of third and fifth order experiments for CdSe colloidal quantum dots. Time constants associated with multiexciton recombination and depopulation dynamics are reported. Deviation from a Poisson model for the distribution of photoexcited excitons, biexcitons, and triexcitons is also discussed.
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Affiliation(s)
- Vanessa M Huxter
- Lash-Miller Chemical Laboratories, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 3H6, Canada
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12
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Kim J, Wong CY, Nair PS, Fritz KP, Kumar S, Scholes GD. Mechanism and Origin of Exciton Spin Relaxation in CdSe Nanorods. J Phys Chem B 2006; 110:25371-82. [PMID: 17165984 DOI: 10.1021/jp0644816] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The dynamics of exciton spin relaxation in CdSe nanorods of various sizes and shapes are measured by an ultrafast transient polarization grating technique. The measurement of the third-order transient grating (3-TG) signal utilizing linear cross-polarized pump pulses enables us to monitor the history of spin relaxation among the bright exciton states with a total angular momentum of F = +/-1. From the measured exciton spin relaxation dynamics, it is found that the effective mechanism of exciton spin relaxation is sensitive to the size of the nanorod. Most of the measured cross-polarized 3-TG signals show single-exponential spin relaxation dynamics, while biexponential spin relaxation dynamics are observed in the nanorod of the largest diameter. This analysis suggests that a direct exciton spin flip process between the bright exciton states with F = +/-1 is the dominant spin relaxation mechanism in small nanocrystals, and an indirect spin flip via the dark states with F = +/-2 contributes as the size of the nanocrystal increases. This idea is examined by simulations of 3-TG signals with a kinetic model for exciton spin relaxation considering the states in the exciton fine structure. Also, it is revealed that the rate of exciton spin relaxation has a strong correlation with the diameter, d, of the nanorod, scaled by the power law of 1/d4, rather than other shape parameters such as length, volume, or aspect ratio.
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Affiliation(s)
- Jeongho Kim
- Lash Miller Chemical Laboratories, Center for Quantum Information and Quantum Control, University of Toronto, Ontario M5S 3H6, Canada
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13
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Scholes GD, Kim J, Wong CY, Huxter VM, Nair PS, Fritz KP, Kumar S. Nanocrystal shape and the mechanism of exciton spin relaxation. NANO LETTERS 2006; 6:1765-71. [PMID: 16895371 DOI: 10.1021/nl061414e] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
The rate of exciton spin relaxation (flips) between the bright exciton states (F = +/-1) of CdSe nanocrystals is reported as a function of shape, for dots and nanorods. The spin relaxation is measured using an ultrafast transient grating method with a crossed linearly polarization sequence. It is found that the spin relaxation rate depends on the radius, not length, of the nanocrystals. That observation is explained by deriving an expression for the electronic coupling matrix element that mixes the bright exciton states.
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Affiliation(s)
- Gregory D Scholes
- Department of Chemistry, 80 St. George Street, Institute for Optical Sciences, and Centre for Quantum Information and Quantum Control, University of Toronto, Toronto, Ontario M5S 3H6 Canada.
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14
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Le Thomas N, Woggon U, Schöps O, Artemyev MV, Kazes M, Banin U. Cavity QED with semiconductor nanocrystals. NANO LETTERS 2006; 6:557-61. [PMID: 16522062 DOI: 10.1021/nl060003v] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
We report on a strongly coupled cavity quantum electrodynamic (CQED) system consisting of a CdSe nanocrystal coupled to a single photon mode of a polymer microsphere. The strong exciton-photon coupling is manifested by the observation of a cavity mode splitting variant Planck's over 2piOmega(exp) between 30 und 45 microeV and photon lifetime measurements of the coupled exciton-photon state. The single photon mode is isolated by lifting the mode degeneracy in a slightly deformed microsphere cavity and addressing it by high-resolution imaging spectroscopy. This cavity mode is coupled to a localized exciton of an anisotropically shaped CdSe nanocrystal that emits highly polarized light in resonance to the cavity mode and that was placed in the maximum electromagnetic field close to the microsphere surface. The exciton confined in the CdSe nanorod exhibits an optical transition dipole moment much larger than that of atoms, the standard system for CQED experiments, and a low-temperature homogeneous line width much narrower than the high-Q cavity mode width. The observation of strong coupling in a colloidal semiconductor nanocrystal-cavity system opens the way to study fundamental quantum-optics phenomena and to implement quantum information processing concepts that work in the visible spectral range and are based on solid-state nanomaterials.
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Affiliation(s)
- N Le Thomas
- Fachbereich Physik, Universität Dortmund, Otto-Hahn-Str. 4, 44227 Dortmund, Germany
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15
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Le Thomas N, Herz E, Schöps O, Woggon U, Artemyev MV. Exciton fine structure in single CdSe nanorods. PHYSICAL REVIEW LETTERS 2005; 94:016803. [PMID: 15698113 DOI: 10.1103/physrevlett.94.016803] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2004] [Indexed: 05/24/2023]
Abstract
We study the optical properties of excitons in one-dimensional (1D) nanostructures at low temperatures. In single CdSe/ZnS core-shell nanorods we observe a fine structure splitting and explain it by exchange interaction. Two peaks are observed with different degrees of linear polarization of DLP<0.85 and DLP>0.95. For small nanorod radii R< or =a(B)/2, an increase in the photoluminescence decay time is found when the temperature increases from 10 to 80 K. The observations are explained by a radius-dependent change in the symmetry of the 1D-exciton ground state which transforms from a dark state into bright states below a critical radius of R(crit) approximately 3.7 nm.
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Affiliation(s)
- N Le Thomas
- Fachbereich Physik, Universität Dortmund, Otto-Hahn-Strasse 4, 44227 Dortmund, Germany
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16
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Labeau O, Tamarat P, Lounis B. Temperature dependence of the luminescence lifetime of single CdSe/ZnS quantum dots. PHYSICAL REVIEW LETTERS 2003; 90:257404. [PMID: 12857165 DOI: 10.1103/physrevlett.90.257404] [Citation(s) in RCA: 140] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2002] [Indexed: 05/22/2023]
Abstract
We study the temperature dependence of the luminescence decay of single CdSe/ZnS quantum dots between 2 and 140 K. For the first time, we observe a biexponential decay which was completely hidden in ensemble measurements. We find that the long time component strongly depends on temperature. This demonstrates that the band edge luminescence arises from two thermally mixed fine structure states, the dark ground state and the lowest bright one. To interpret our results, we derive the analytical expressions for the decay using a three level model. Fitting the experimental data leads directly to the lifetime of the states as well as their energy splitting.
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Affiliation(s)
- Olivier Labeau
- Centre de Physique Moléculaire Optique et Hertzienne, CNRS, 351 Cours de la Libération, 33405 Talence Cedex, France
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17
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Gavartin JL, Stoneham AM. Quantum dots as dynamical systems. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2003; 361:275-290. [PMID: 12639383 DOI: 10.1098/rsta.2002.1128] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Quantum dots show a range of time-dependent behaviours. We show that the polarity of II-VI nanoparticles has important dynamical implications for electronic, vibrational and other phenomena. Polarity-dependent phenomena are found even for nearly spherical stoichiometric clusters of ZnO and ZnS in studies based on interatomic potentials or on a plane-wave density-functional approach. We find a substantial dipole moment for free nanoparticles, whether of the zinc blende or wurtzite structure. This dipole causes a highly non-uniform spin-density distribution on electronic excitation or after a change in the dot's electronic charge state. The spin density of the triplet exciton shows that the dipole aligns so as to reduce the dipole moment in the electronically excited state. The polarity of II-VI dots also affects their vibrational properties. High- and low-frequency tails of the vibration density of states arise from modes strongly localized at surface atoms, near the poles of the dipole. These features, first noted for free clusters, also hold for particles embedded in a wide-gap dielectric, a-SiO(2). We present the results of molecular dynamics of the ZnS particle embedded into the silica glass, and consider the role played by the soft modes in energy-dissipation processes such as dephasing during non-radiative recombination of excitons, and energy transfer from the dot to the matrix.
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Affiliation(s)
- J L Gavartin
- Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK.
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18
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Kuno M, Nirmal M, Bawendi MG, Efros A, Rosen M. Magnetic circular dichroism study of CdSe quantum dots. J Chem Phys 1998. [DOI: 10.1063/1.475823] [Citation(s) in RCA: 74] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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19
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20
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21
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Ptatschek V, Schreder B, Herz K, Hilbert U, Ossau W, Schottner G, Rahäuser O, Bischof T, Lermann G, Materny A, Kiefer W, Bacher G, Forchel A, Su D, Giersig M, Müller G, Spanhel L. Sol−Gel Synthesis and Spectroscopic Properties of Thick Nanocrystalline CdSe Films. J Phys Chem B 1997. [DOI: 10.1021/jp971487+] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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22
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Mićić OI, Cheong HM, Fu H, Zunger A, Sprague JR, Mascarenhas A, Nozik AJ. Size-Dependent Spectroscopy of InP Quantum Dots. J Phys Chem B 1997. [DOI: 10.1021/jp9704731] [Citation(s) in RCA: 317] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- O. I. Mićić
- National Renewable Energy Laboratory, 1617 Cole Boulevard, Golden, Colorado 80401
| | - H. M. Cheong
- National Renewable Energy Laboratory, 1617 Cole Boulevard, Golden, Colorado 80401
| | - H. Fu
- National Renewable Energy Laboratory, 1617 Cole Boulevard, Golden, Colorado 80401
| | - A. Zunger
- National Renewable Energy Laboratory, 1617 Cole Boulevard, Golden, Colorado 80401
| | - J. R. Sprague
- National Renewable Energy Laboratory, 1617 Cole Boulevard, Golden, Colorado 80401
| | - A. Mascarenhas
- National Renewable Energy Laboratory, 1617 Cole Boulevard, Golden, Colorado 80401
| | - A. J. Nozik
- National Renewable Energy Laboratory, 1617 Cole Boulevard, Golden, Colorado 80401
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Schmidt ME, Blanton SA, Hines MA, Guyot-Sionnest P. Polar CdSe nanocrystals: Implications for electronic structure. J Chem Phys 1997. [DOI: 10.1063/1.473524] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Woggon U, Giessen H, Gindele F, Wind O, Fluegel B, Peyghambarian N. Ultrafast energy relaxation in quantum dots. PHYSICAL REVIEW. B, CONDENSED MATTER 1996; 54:17681-17690. [PMID: 9985896 DOI: 10.1103/physrevb.54.17681] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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