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Excitonic Zeeman splittings in colloidal CdSe quantum dots doped with single magnetic impurities

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Abstract

Doping a semiconductor quantum dot with just a single impurity atom can completely transform its physical properties. Here, we report and analyze the magnetic circular dichroism (MCD) spectra of colloidal CdSe quantum dot samples containing on average fewer than one Mn2+ per quantum dot. Even at this sub-single-dopant level, the low-temperature low-field data are dominated by impurity-induced Zeeman splittings caused by dopant–carrier sp–d exchange. Unlike in more heavily doped quantum dots, however, the MCD intensity at the first CdSe exciton shows a field-induced sign flip as the field strength is increased, reflecting competition between sp–d exchange and the intrinsic Zeeman splittings of comparable magnitude. Most unusually, the competition between these two effects leads to a large apparent shift in the first MCD peak maximum, which we show is attributable to a difference in sign of the intrinsic excitonic g factor between the first and second excitons. Finally, the sp–d and intrinsic contributions to the excitonic Zeeman splittings each exhibit unique magnetic-field and temperature dependencies, allowing the MCD spectra of undoped, singly doped, and bi-doped quantum dot sub-ensembles to be analyzed.

Graphical abstract: Excitonic Zeeman splittings in colloidal CdSe quantum dots doped with single magnetic impurities

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Publication details

The article was received on 09 Mar 2017, accepted on 15 May 2017 and first published on 16 May 2017


Article type: Paper
DOI: 10.1039/C7TC01007A
Citation: J. Mater. Chem. C, 2017, Advance Article
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    Excitonic Zeeman splittings in colloidal CdSe quantum dots doped with single magnetic impurities

    C. J. Barrows, R. Fainblat and D. R. Gamelin, J. Mater. Chem. C, 2017, Advance Article , DOI: 10.1039/C7TC01007A

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