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Plasmon-induced carrier polarization in semiconductor nanocrystals


Spintronics1 and valleytronics2 are emerging quantum electronic technologies that rely on using electron spin and multiple extrema of the band structure (valleys), respectively, as additional degrees of freedom. There are also collective properties of electrons in semiconductor nanostructures that potentially could be exploited in multifunctional quantum devices. Specifically, plasmonic semiconductor nanocrystals3,4,5,6,7,8,9,10 offer an opportunity for interface-free coupling between a plasmon and an exciton. However, plasmon–exciton coupling in single-phase semiconductor nanocrystals remains challenging because confined plasmon oscillations are generally not resonant with excitonic transitions. Here, we demonstrate a robust electron polarization in degenerately doped In2O3 nanocrystals, enabled by non-resonant coupling of cyclotron magnetoplasmonic modes11 with the exciton at the Fermi level. Using magnetic circular dichroism spectroscopy, we show that intrinsic plasmon–exciton coupling allows for the indirect excitation of the magnetoplasmonic modes, and subsequent Zeeman splitting of the excitonic states. Splitting of the band states and selective carrier polarization can be manipulated further by spin–orbit coupling. Our results effectively open up the field of plasmontronics, which involves the phenomena that arise from intrinsic plasmon–exciton and plasmon–spin interactions. Furthermore, the dynamic control of carrier polarization is readily achieved at room temperature, which allows us to harness the magnetoplasmonic mode as a new degree of freedom in practical photonic, optoelectronic and quantum-information processing devices.

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Fig. 1: Absorption and MCD of LSPR in semiconductor nanocrystals.
Fig. 2: Electron polarization by magnetoplasmonic modes in ITO nanocrystals.
Fig. 3: Spin-induced manipulation of Zeeman splitting in plasmonic IMO nanocrystals.
Fig. 4: Control of the charge carrier polarization in IMO nanocrystals.

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We acknowledge the financial support from the Natural Sciences and Engineering Research Council of Canada (NSERC) (RGPIN-2015-67304032), Canada Foundation for Innovation (Project no. 204782) and the University of Waterloo (UW-Bordeaux Collaborative Research Grant). This research was undertaken thanks, in part, to funding from the Canada First Research Excellence Fund. P.V.R. acknowledges the support from the Canada Research Chairs Program (NSERC).

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Authors and Affiliations



P.Y. and P.V.R. designed the experiments. P.Y., Y.T. and H.F. prepared and characterized the samples. P.Y. and Y.T. conducted MCD measurements. P.Y. analysed the data. M.H. performed the DFT calculations and analysis. P.V.R. and P.Y. interpreted the results and wrote the manuscript with contributions from the other authors. P.V.R. conceived and supervised the project.

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Correspondence to Pavle V. Radovanovic.

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Yin, P., Tan, Y., Fang, H. et al. Plasmon-induced carrier polarization in semiconductor nanocrystals. Nature Nanotech 13, 463–467 (2018).

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