Light-induced magnetism in plasmonic gold nanoparticles


Strategies for the ultrafast optical control of magnetism have been a topic of intense research for several decades because of the potential impact in technologies such as magnetic memory1, spintronics2 and quantum computation, as well as the opportunities for nonlinear optical control and modulation3 in applications such as optical isolation and non-reciprocity4. Here we report experimental quantification of optically induced magnetization in plasmonic gold nanoparticles due to the inverse Faraday effect. The induced magnetic moment is large under typical ultrafast pulse excitation (<1014 W m−2 peak intensity), with magnetization and demagnetization kinetics that are instantaneous within the subpicosecond time resolution of our study. Our results support a mechanism of coherent transfer of angular momentum from the optical field to the electron gas, and open the door to all-optical subwavelength strategies for optical isolation that do not require externally applied magnetic fields.

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Fig. 1: Schematic of the Faraday effect and the IFE in AuNP colloids.
Fig. 2: Static Faraday rotation of 100-nm-diameter AuNPs.
Fig. 3: Time-resolved pump–probe IFE experiment on 100-nm-diameter AuNPs.
Fig. 4: IFE experiment with counter-propagating pump and probe beams.
Fig. 5: Dependence of optical rotation on pump intensity for case II and the corresponding effective magnetic field.

Data availability

Source data for Figs. 25 are provided. All other data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.


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We acknowledge the technical support of D. Rossi. This work was funded in part by the Gordon and Betty Moore Foundation through grant no. GBMF6882 and by the Air Force Office of Scientific Research under award no. FA9550-16-1-0154. M.S. also acknowledges support from the Welch Foundation (A-1886). D.H.S. appreciates support from the Institute for Basic Science (IBS-R026-D1).

Author information




O.H.-C.C. carried out the measurements and analysed the data. D.H.S. and M.S. supervised the project and participated in the analysis of the data.

Corresponding authors

Correspondence to Dong Hee Son or Matthew Sheldon.

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Supplementary information

Supplementary Information

Supplementary Figs. 1–3, Discussion Sections 1–8 and Table 1.

Source data

Source Data Fig. 2

Numerical data for extinction spectra and Faraday rotation.

Source Data Fig. 3

Numerical data for figure.

Source Data Fig. 4

Numerical data for figure.

Source Data Fig. 5

Numerical data for figure.

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Cheng, O.H., Son, D.H. & Sheldon, M. Light-induced magnetism in plasmonic gold nanoparticles. Nat. Photonics 14, 365–368 (2020).

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