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Mattioni A, Staab JK, Blackmore WJA, Reta D, Iles-Smith J, Nazir A, Chilton NF. Vibronic effects on the quantum tunnelling of magnetisation in Kramers single-molecule magnets. Nat Commun 2024; 15:485. [PMID: 38212305 PMCID: PMC10784566 DOI: 10.1038/s41467-023-44486-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Accepted: 12/13/2023] [Indexed: 01/13/2024] Open
Abstract
Single-molecule magnets are among the most promising platforms for achieving molecular-scale data storage and processing. Their magnetisation dynamics are determined by the interplay between electronic and vibrational degrees of freedom, which can couple coherently, leading to complex vibronic dynamics. Building on an ab initio description of the electronic and vibrational Hamiltonians, we formulate a non-perturbative vibronic model of the low-energy magnetic degrees of freedom in monometallic single-molecule magnets. Describing their low-temperature magnetism in terms of magnetic polarons, we are able to quantify the vibronic contribution to the quantum tunnelling of the magnetisation, a process that is commonly assumed to be independent of spin-phonon coupling. We find that the formation of magnetic polarons lowers the tunnelling probability in both amorphous and crystalline systems by stabilising the low-lying spin states. This work, thus, shows that spin-phonon coupling subtly influences magnetic relaxation in single-molecule magnets even at extremely low temperatures where no vibrational excitations are present.
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Affiliation(s)
- Andrea Mattioni
- Department of Chemistry, School of Natural Sciences, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK.
| | - Jakob K Staab
- Department of Chemistry, School of Natural Sciences, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK
| | - William J A Blackmore
- Department of Chemistry, School of Natural Sciences, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK
| | - Daniel Reta
- Department of Chemistry, School of Natural Sciences, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK
- Faculty of Chemistry, The University of the Basque Country UPV/EHU, Donostia, 20018, Spain
- Donostia International Physics Center (DIPC), Donostia, 20018, Spain
- IKERBASQUE, Basque Foundation for Science, Bilbao, 48013, Spain
| | - Jake Iles-Smith
- Department of Physics and Astronomy, School of Natural Sciences, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK
| | - Ahsan Nazir
- Department of Physics and Astronomy, School of Natural Sciences, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK
| | - Nicholas F Chilton
- Department of Chemistry, School of Natural Sciences, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK.
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2
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Babunts RA, Uspenskaya YA, Romanov NG, Orlinskii SB, Mamin GV, Shornikova EV, Yakovlev DR, Bayer M, Isik F, Shendre S, Delikanli S, Demir HV, Baranov PG. High-Frequency EPR and ENDOR Spectroscopy of Mn 2+ Ions in CdSe/CdMnS Nanoplatelets. ACS NANO 2023; 17:4474-4482. [PMID: 36802485 DOI: 10.1021/acsnano.2c10123] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Semiconductor colloidal nanoplatelets based of CdSe have excellent optical properties. Their magneto-optical and spin-dependent properties can be greatly modified by implementing magnetic Mn2+ ions, using concepts well established for diluted magnetic semiconductors. A variety of magnetic resonance techniques based on high-frequency (94 GHz) electron paramagnetic resonance in continuous wave and pulsed mode were used to get detailed information on the spin structure and spin dynamics of Mn2+ ions in core/shell CdSe/(Cd,Mn)S nanoplatelets. We observed two sets of resonances assigned to the Mn2+ ions inside the shell and at the nanoplatelet surface. The surface Mn demonstrates a considerably longer spin dynamics than the inner Mn due to lower amount of surrounding Mn2+ ions. The interaction between surface Mn2+ ions and 1H nuclei belonging to oleic acid ligands is measured by means of electron nuclear double resonance. This allowed us to estimate the distances between the Mn2+ ions and 1H nuclei, which equal to 0.31 ± 0.04, 0.44 ± 0.09, and more than 0.53 nm. This study shows that the Mn2+ ions can serve as atomic-size probes for studying the ligand attachment to the nanoplatelet surface.
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Affiliation(s)
- Roman A Babunts
- Ioffe Institute, Russian Academy of Sciences, 194021 St. Petersburg, Russia
| | - Yulia A Uspenskaya
- Ioffe Institute, Russian Academy of Sciences, 194021 St. Petersburg, Russia
| | - Nikolai G Romanov
- Ioffe Institute, Russian Academy of Sciences, 194021 St. Petersburg, Russia
| | | | - Georgy V Mamin
- Kazan Federal University, Institute of Physics, 420008 Kazan, Russia
| | - Elena V Shornikova
- Experimentelle Physik 2, Technische Universität Dortmund, 44227 Dortmund, Germany
| | - Dmitri R Yakovlev
- Ioffe Institute, Russian Academy of Sciences, 194021 St. Petersburg, Russia
- Experimentelle Physik 2, Technische Universität Dortmund, 44227 Dortmund, Germany
| | - Manfred Bayer
- Experimentelle Physik 2, Technische Universität Dortmund, 44227 Dortmund, Germany
| | - Furkan Isik
- Department of Electrical and Electronics Engineering, Department of Physics, UNAM - Institute of Materials Science and Nanotechnology, Bilkent University, 06800 Ankara, Turkey
| | - Sushant Shendre
- Luminous! Center of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering, Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, School of Materials Science and Engineering, Nanyang Technological University, 639798 Singapore
| | - Savas Delikanli
- Luminous! Center of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering, Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, School of Materials Science and Engineering, Nanyang Technological University, 639798 Singapore
- Department of Electrical and Electronics Engineering, Department of Physics, UNAM - Institute of Materials Science and Nanotechnology, Bilkent University, 06800 Ankara, Turkey
| | - Hilmi Volkan Demir
- Luminous! Center of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering, Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, School of Materials Science and Engineering, Nanyang Technological University, 639798 Singapore
- Department of Electrical and Electronics Engineering, Department of Physics, UNAM - Institute of Materials Science and Nanotechnology, Bilkent University, 06800 Ankara, Turkey
| | - Pavel G Baranov
- Ioffe Institute, Russian Academy of Sciences, 194021 St. Petersburg, Russia
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3
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Guan X, Srivastava S, Thomas JP, Heinig NF, Kang JS, Rahman MA, Leung KT. Defect-Rich Dopant-Free ZrO 2 Nanoclusters and Their Size-Dependent Ferromagnetism. ACS APPLIED MATERIALS & INTERFACES 2020; 12:48998-49005. [PMID: 33063993 DOI: 10.1021/acsami.0c14706] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
As an intermediate form of matter between a single atom or molecule and the bulk, nanoclusters (NCs) provide novel properties because of their high surface area-to-volume ratios and distinct physical and electronic structures. These ultrasmall NCs offer a new approach to advance charge-spin manipulation for novel devices, including spintronics and magnetic tunneling junctions. Here, we deposit monosized ZrO2 NCs over a large area by using gas-phase aggregation followed by in situ size selection by a quadrupole mass filter. These size-specific NCs exhibit sub-oxide photoemission features at binding energies that are dependent on the cluster size (from 3 to 9 nm), which are attributed to different oxygen vacancy defect states. These dopant-free ZrO2 NCs also show strongly size-dependent ferromagnetism, which provides distinct advantages in solubility and homogeneity of magnetism when compared to traditional dilute magnetic semiconductors. A defect-band hybridization-induced magnetic polaron model is proposed to explain the origin of this size-dependent ferromagnetism. This work demonstrates a new protocol of magnetization manipulation by size control and promises potential applications based on these defect-rich size-selected NCs.
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Affiliation(s)
- Xiaoyi Guan
- WATLab and Department of Chemistry, University of Waterloo, 200 University Ave. W., Waterloo, Ontario N2L 3G1, Canada
| | - Saurabh Srivastava
- WATLab and Department of Chemistry, University of Waterloo, 200 University Ave. W., Waterloo, Ontario N2L 3G1, Canada
| | - Joseph Palathinkal Thomas
- WATLab and Department of Chemistry, University of Waterloo, 200 University Ave. W., Waterloo, Ontario N2L 3G1, Canada
| | - Nina F Heinig
- WATLab and Department of Chemistry, University of Waterloo, 200 University Ave. W., Waterloo, Ontario N2L 3G1, Canada
| | - Jung-Soo Kang
- WATLab and Department of Chemistry, University of Waterloo, 200 University Ave. W., Waterloo, Ontario N2L 3G1, Canada
| | - Md Anisur Rahman
- WATLab and Department of Chemistry, University of Waterloo, 200 University Ave. W., Waterloo, Ontario N2L 3G1, Canada
| | - Kam Tong Leung
- WATLab and Department of Chemistry, University of Waterloo, 200 University Ave. W., Waterloo, Ontario N2L 3G1, Canada
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4
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Dehnel J, Barak Y, Meir I, Budniak AK, Nagvenkar AP, Gamelin DR, Lifshitz E. Insight into the Spin Properties in Undoped and Mn-Doped CdSe/CdS-Seeded Nanorods by Optically Detected Magnetic Resonance. ACS NANO 2020; 14:13478-13490. [PMID: 32935976 DOI: 10.1021/acsnano.0c05454] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Controlling the spin degrees of freedom of photogenerated species in semiconductor nanostructures via magnetic doping is an emerging scientific field that may play an important role in the development of new spin-based technologies. The current work explores spin properties in colloidal CdSe/CdS:Mn seeded-nanorod structures doped with a dilute concentration of Mn2+ ions across the rods. The spin properties were determined using continuous-wave optically detected magnetic resonance (ODMR) spectroscopy recorded under variable microwave chopping frequencies. These experiments enabled the deconvolution of a few different radiative recombination processes: band-to-band, trap-to-band, and trap-to-trap emission. The results uncovered the major role of carrier trapping on the spin properties of elongated structures. The magnetic parameters, determined through spin-Hamiltonian simulation of the steady-state ODMR spectra, reflect anisotropy associated with carrier trapping at the seed/rod interface. These observations unveiled changes in the carriers' g-factors and spin-exchange coupling constants as well as extension of radiative and spin-lattice relaxation times due to magnetic coupling between interface carriers and neighboring Mn2+ ions. Overall, this work highlights that the spin degrees of freedom in seeded nanorods are governed by interfacial trapping and can be further manipulated by magnetic doping. These results provide insights into anisotropic nanostructure spin properties relevant to future spin-based technologies.
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Affiliation(s)
- Joanna Dehnel
- Schulich Faculty of Chemistry, Solid State Institute, Russell Berrie Nanotechnology Institute, Technion-Israel Institute of Technology, Haifa 3200003, Israel
| | - Yahel Barak
- Schulich Faculty of Chemistry, Solid State Institute, Russell Berrie Nanotechnology Institute, Technion-Israel Institute of Technology, Haifa 3200003, Israel
| | - Itay Meir
- Schulich Faculty of Chemistry, Solid State Institute, Russell Berrie Nanotechnology Institute, Technion-Israel Institute of Technology, Haifa 3200003, Israel
| | - Adam K Budniak
- Schulich Faculty of Chemistry, Solid State Institute, Russell Berrie Nanotechnology Institute, Technion-Israel Institute of Technology, Haifa 3200003, Israel
| | - Anjani P Nagvenkar
- Schulich Faculty of Chemistry, Solid State Institute, Russell Berrie Nanotechnology Institute, Technion-Israel Institute of Technology, Haifa 3200003, Israel
| | - Daniel R Gamelin
- Department of Chemistry and the Molecular Engineering Materials Center, University of Washington, Box 351700, Seattle, Washington 98195-1700, United States
| | - Efrat Lifshitz
- Schulich Faculty of Chemistry, Solid State Institute, Russell Berrie Nanotechnology Institute, Technion-Israel Institute of Technology, Haifa 3200003, Israel
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5
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Lorenz S, Erickson CS, Riesner M, Gamelin DR, Fainblat R, Bacher G. Directed Exciton Magnetic Polaron Formation in a Single Colloidal Mn 2+:CdSe/CdS Quantum Dot. NANO LETTERS 2020; 20:1896-1906. [PMID: 31999124 DOI: 10.1021/acs.nanolett.9b05136] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
One of the most prominent signatures of transition-metal doping in colloidal nanocrystals is the formation of charge carrier-induced magnetization of the dopant spin sublattice, called exciton magnetic polaron (EMP). Understanding the direction of EMP formation, however, is still a major obstacle. Here, we present a series of temperature-dependent photoluminescence studies on single colloidal Mn2+:CdSe/CdS core/shell quantum dots (QDs) performed in a vector magnetic field providing a unique insight into the interaction between individual excitons and numerous magnetic impurities. The energy of the QD emission and its full width at half-maximum are controlled by the interplay of EMP formation and statistical magnetic fluctuations, in excellent agreement with theory. Most important, we give the first direct demonstration that anisotropy effects-hypothesized for more than a decade-dominate the direction of EMP formation. Our findings reveal a pathway for directing the orientation of optically induced magnetization in colloidal nanocrystals.
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Affiliation(s)
- Severin Lorenz
- Werkstoffe der Elektrotechnik and CENIDE, University of Duisburg-Essen, Bismarckstr. 81, Duisburg 47057 Germany
| | - Christian S Erickson
- Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, United States
| | - Maurizio Riesner
- Werkstoffe der Elektrotechnik and CENIDE, University of Duisburg-Essen, Bismarckstr. 81, Duisburg 47057 Germany
| | - Daniel R Gamelin
- Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, United States
| | - Rachel Fainblat
- Werkstoffe der Elektrotechnik and CENIDE, University of Duisburg-Essen, Bismarckstr. 81, Duisburg 47057 Germany
| | - Gerd Bacher
- Werkstoffe der Elektrotechnik and CENIDE, University of Duisburg-Essen, Bismarckstr. 81, Duisburg 47057 Germany
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6
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Strassberg R, Delikanli S, Barak Y, Dehnel J, Kostadinov A, Maikov G, Hernandez-Martinez PL, Sharma M, Demir HV, Lifshitz E. Persuasive Evidence for Electron-Nuclear Coupling in Diluted Magnetic Colloidal Nanoplatelets Using Optically Detected Magnetic Resonance Spectroscopy. J Phys Chem Lett 2019; 10:4437-4447. [PMID: 31314537 DOI: 10.1021/acs.jpclett.9b01999] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The incorporation of magnetic impurities into semiconductor nanocrystals with size confinement promotes enhanced spin exchange interaction between photogenerated carriers and the guest spins. This interaction stimulates new magneto-optical properties with significant advantages for emerging spin-based technologies. Here we observe and elaborate on carrier-guest interactions in magnetically doped colloidal nanoplatelets with the chemical formula CdSe/Cd1-xMnxS, explored by optically detected magnetic resonance and magneto-photoluminescence spectroscopy. The host matrix, with a quasi-type II electronic configuration, introduces a dominant interaction between a photogenerated electron and a magnetic dopant. Furthermore, the data convincingly presents the interaction between an electron and nuclear spins of the doped ions located at neighboring surroundings, with consequent influence on the carrier's spin relaxation time. The nuclear spin contribution by the magnetic dopants in colloidal nanoplatelets is considered here for the first time.
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Affiliation(s)
- Rotem Strassberg
- Schulich Faculty of Chemistry, Solid State Institute, Russell Berrie Nanotechnology Institute , Technion-Israel Institute of Technology , Haifa 32000 , Israel
| | - Savas Delikanli
- Luminous Center of Excellence for Semiconductor Lighting and Displays, TPI, School of Electrical and Electronic Engineering, School of Physical and Mathematical Sciences, School of Materials Science and Engineering , Nanyang Technological University-NTU Singapore , 639798 Singapore
- Department of Electrical and Electronics Engineering, Department of Physics, UNAM-Institute of Materials Science and Nanotechnology , Bilkent University , Ankara 06800 , Turkey
| | - Yahel Barak
- Schulich Faculty of Chemistry, Solid State Institute, Russell Berrie Nanotechnology Institute , Technion-Israel Institute of Technology , Haifa 32000 , Israel
| | - Joanna Dehnel
- Schulich Faculty of Chemistry, Solid State Institute, Russell Berrie Nanotechnology Institute , Technion-Israel Institute of Technology , Haifa 32000 , Israel
| | - Alyssa Kostadinov
- Schulich Faculty of Chemistry, Solid State Institute, Russell Berrie Nanotechnology Institute , Technion-Israel Institute of Technology , Haifa 32000 , Israel
| | - Georgy Maikov
- Schulich Faculty of Chemistry, Solid State Institute, Russell Berrie Nanotechnology Institute , Technion-Israel Institute of Technology , Haifa 32000 , Israel
| | - Pedro Ludwig Hernandez-Martinez
- Luminous Center of Excellence for Semiconductor Lighting and Displays, TPI, School of Electrical and Electronic Engineering, School of Physical and Mathematical Sciences, School of Materials Science and Engineering , Nanyang Technological University-NTU Singapore , 639798 Singapore
| | - Manoj Sharma
- Luminous Center of Excellence for Semiconductor Lighting and Displays, TPI, School of Electrical and Electronic Engineering, School of Physical and Mathematical Sciences, School of Materials Science and Engineering , Nanyang Technological University-NTU Singapore , 639798 Singapore
- Department of Electrical and Electronics Engineering, Department of Physics, UNAM-Institute of Materials Science and Nanotechnology , Bilkent University , Ankara 06800 , Turkey
| | - Hilmi Volkan Demir
- Luminous Center of Excellence for Semiconductor Lighting and Displays, TPI, School of Electrical and Electronic Engineering, School of Physical and Mathematical Sciences, School of Materials Science and Engineering , Nanyang Technological University-NTU Singapore , 639798 Singapore
- Department of Electrical and Electronics Engineering, Department of Physics, UNAM-Institute of Materials Science and Nanotechnology , Bilkent University , Ankara 06800 , Turkey
| | - Efrat Lifshitz
- Schulich Faculty of Chemistry, Solid State Institute, Russell Berrie Nanotechnology Institute , Technion-Israel Institute of Technology , Haifa 32000 , Israel
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7
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Biadala L, Shornikova EV, Rodina AV, Yakovlev DR, Siebers B, Aubert T, Nasilowski M, Hens Z, Dubertret B, Efros AL, Bayer M. Magnetic polaron on dangling-bond spins in CdSe colloidal nanocrystals. NATURE NANOTECHNOLOGY 2017; 12:569-574. [PMID: 28288118 DOI: 10.1038/nnano.2017.22] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2016] [Accepted: 02/02/2017] [Indexed: 05/22/2023]
Abstract
Non-magnetic colloidal nanostructures can demonstrate magnetic properties typical for diluted magnetic semiconductors because the spins of dangling bonds at their surface can act as the localized spins of magnetic ions. Here we report the observation of dangling-bond magnetic polarons (DBMPs) in 2.8-nm diameter CdSe colloidal nanocrystals (NCs). The DBMP binding energy of 7 meV is measured from the spectral shift of the emission lines under selective laser excitation. The polaron formation at low temperatures occurs by optical orientation of the dangling-bond spins (DBSs) that result from dangling-bond-assisted radiative recombination of spin-forbidden dark excitons. Modelling of the temperature dependence of the DBMP-binding energy and emission intensity shows that the DBMP is composed of a dark exciton and about 60 DBSs. The exchange integral of one DBS with the electron confined in the NC is ∼0.12 meV.
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Affiliation(s)
- Louis Biadala
- Experimentelle Physik 2, Technische Universität Dortmund, 44227 Dortmund, Germany
- IEMN, CNRS, Avenue Henri Poincaré, 59491 Villeneuve-d'Ascq, France
| | - Elena V Shornikova
- Experimentelle Physik 2, Technische Universität Dortmund, 44227 Dortmund, Germany
- Rzhanov Institute of Semiconductor Physics, Siberian Branch of Russian Academy of Sciences, 630090 Novosibirsk, Russia
| | - Anna V Rodina
- Ioffe Institute, Russian Academy of Sciences, 194021 Saint Petersburg, Russia
| | - Dmitri R Yakovlev
- Experimentelle Physik 2, Technische Universität Dortmund, 44227 Dortmund, Germany
- Ioffe Institute, Russian Academy of Sciences, 194021 Saint Petersburg, Russia
| | - Benjamin Siebers
- Experimentelle Physik 2, Technische Universität Dortmund, 44227 Dortmund, Germany
| | - Tangi Aubert
- Department of Inorganic and Physical Chemistry, Universiteit Gent, 9000 Ghent, Belgium
| | - Michel Nasilowski
- Laboratoire de Physique et d'Etude des Matériaux, PSL Research University, CNRS UMR 8213, Sorbonne Universités UPMC Université Paris 06, ESPCI Paris, 10 rue Vauquelin, 75005 Paris, France
| | - Zeger Hens
- Department of Inorganic and Physical Chemistry, Universiteit Gent, 9000 Ghent, Belgium
| | - Benoit Dubertret
- Laboratoire de Physique et d'Etude des Matériaux, PSL Research University, CNRS UMR 8213, Sorbonne Universités UPMC Université Paris 06, ESPCI Paris, 10 rue Vauquelin, 75005 Paris, France
| | | | - Manfred Bayer
- Experimentelle Physik 2, Technische Universität Dortmund, 44227 Dortmund, Germany
- Ioffe Institute, Russian Academy of Sciences, 194021 Saint Petersburg, Russia
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8
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Nelson HD, Bradshaw LR, Barrows CJ, Vlaskin VA, Gamelin DR. Picosecond Dynamics of Excitonic Magnetic Polarons in Colloidal Diffusion-Doped Cd(1-x)Mn(x)Se Quantum Dots. ACS NANO 2015; 9:11177-11191. [PMID: 26417918 DOI: 10.1021/acsnano.5b04719] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Spontaneous magnetization is observed at zero magnetic field in photoexcited colloidal Cd(1-x)Mn(x)Se (x = 0.13) quantum dots (QDs) prepared by diffusion doping, reflecting strong Mn(2+)-exciton exchange coupling. The picosecond dynamics of this phenomenon, known as an excitonic magnetic polaron (EMP), are examined using a combination of time-resolved photoluminescence, magneto-photoluminescence, and Faraday rotation (TRFR) spectroscopies, in conjunction with continuous-wave absorption, magnetic circular dichroism (MCD), and magnetic circularly polarized photoluminescence (MCPL) spectroscopies. The data indicate that EMPs form with random magnetization orientations at zero external field, but their formation can be directed by an external magnetic field. After formation, however, external magnetic fields are unable to reorient the EMPs within the luminescence lifetime, implicating anisotropy in the EMP potential-energy surfaces. TRFR measurements in a transverse magnetic field reveal rapid (<5 ps) spin transfer from excitons to Mn(2+) followed by coherent EMP precession at the Mn(2+) Larmor frequency for over a nanosecond. A dynamical TRFR phase inversion is observed during EMP formation attributed to the large shifts in excitonic absorption energies during spontaneous magnetization. Partial optical orientation of the EMPs by resonant circularly polarized photoexcitation is also demonstrated. Collectively, these results highlight the extraordinary physical properties of colloidal diffusion-doped Cd(1-x)Mn(x)Se QDs that result from their unique combination of strong quantum confinement, large Mn(2+) concentrations, and relatively narrow size distributions. The insights gained from these measurements advance our understanding of spin dynamics and magnetic exchange in colloidal doped semiconductor nanostructures, with potential ramifications for future spin-based information technologies.
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Affiliation(s)
- Heidi D Nelson
- Department of Chemistry, University of Washington , Seattle, Washington 98195-1700, United States
| | - Liam R Bradshaw
- Department of Chemistry, University of Washington , Seattle, Washington 98195-1700, United States
| | - Charles J Barrows
- Department of Chemistry, University of Washington , Seattle, Washington 98195-1700, United States
| | - Vladimir A Vlaskin
- Department of Chemistry, University of Washington , Seattle, Washington 98195-1700, United States
| | - Daniel R Gamelin
- Department of Chemistry, University of Washington , Seattle, Washington 98195-1700, United States
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9
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Rodina A, Efros AL. Magnetic Properties of Nonmagnetic Nanostructures: Dangling Bond Magnetic Polaron in CdSe Nanocrystals. NANO LETTERS 2015; 15:4214-4222. [PMID: 25919576 DOI: 10.1021/acs.nanolett.5b01566] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We predict theoretically that nonmagnetic CdSe nanocrystals may possess macroscopic magnetic moments due to the formation of dangling-bond magnetic polarons (DBMPs). A DBMP is created in optically pumped nanocrystals by dynamic polarization of dangling bond spins (DBSs) at the nanocrystal surface during radiative recombination of the ground state "dark" exciton assisted by a spin-flip of the DBS. The formation of DBMPs suppresses the radiative recombination of the dark exciton and leads to a temperature-dependent contribution to the Stokes shift of the photoluminescence. This model consistently explains the experimentally observed low-temperature photoluminescence features of nonmagnetic CdSe nanocrystals as manifestations of their spin-related magnetic properties.
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Affiliation(s)
- Anna Rodina
- †Ioffe Physical-Technical Institute, Russian Academy of Sciences, 194021 St. Petersburg, Russia
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10
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Chernenko AV, Brichkin AS. Localized and bound excitons in type-II ZnMnSe/ZnSSe quantum wells. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:425301. [PMID: 25273841 DOI: 10.1088/0953-8984/26/42/425301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Photoluminescence of ZnMnSe/ZnSSe multiple quantum wells under a bandgap continuous wave and fs-pulsed excitations is measured in magnetic fields up to 10 T in Faraday geometry at temperatures within the range of 1.6-20 K. The measurements reveal two dominant lines in the spectra and LO-phonon replicas of the lower-energy line. The photoluminescence and time-resolved studies show dramatically different behaviour of the lines. Analysis of their properties reveals that they correspond to recombination of indirect localized excitons and indirect acceptor-bound excitons (A0X). Crossing of exciton and A0X lines because of the difference in magnitudes of their Zeeman shifts is observed. Analysis of LO-phonon replicas of photoluminescence lines provides additional evidence for strong carrier localization bound to A0X. A model of phonon-assisted recombination of indirect acceptor-bound excitons is proposed. The fitting of photoluminescence lines with this model gives the Huang-Rhys factor S≃0.25 for A0X and the hole localization size ah≃30 Å. Contrary to expectations the exciton magnetic polaron effect is hardly observed in these structures.
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Affiliation(s)
- A V Chernenko
- Institute of Solid State Physics, RAS, 142432, Chernogolovka, Russia
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