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Gate-tunable spin waves in antiferromagnetic atomic bilayers

Abstract

Remarkable properties of two-dimensional (2D) layer magnetic materials, which include spin filtering in magnetic tunnel junctions and the gate control of magnetic states, were demonstrated recently1,2,3,4,5,6,7,8,9,10,11,12. Whereas these studies focused on static properties, dynamic magnetic properties, such as excitation and control of spin waves, remain elusive. Here we investigate spin-wave dynamics in antiferromagnetic CrI3 bilayers using an ultrafast optical pump/magneto-optical Kerr probe technique. Monolayer WSe2 with a strong excitonic resonance was introduced on CrI3 to enhance the optical excitation of spin waves. We identified subterahertz magnetic resonances under an in-plane magnetic field, from which the anisotropy and interlayer exchange fields were determined. We further showed tuning of the antiferromagnetic resonances by tens of gigahertz through electrostatic gating. Our results shed light on magnetic excitations and spin dynamics in 2D magnetic materials, and demonstrate their potential for applications in ultrafast data storage and processing.

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Fig. 1: Bilayer CrI3–monolayer WSe2 heterostructures.
Fig. 2: Time-resolved magnon oscillations.
Fig. 3: Magnon dispersion and damping.
Fig. 4: Gate tunable magnon frequencies.

Data availability

The data that support the findings of this study are available within the paper and its Supplementary Information. Additional data are available from the corresponding authors upon request.

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Acknowledgements

This work was supported by the National Science Foundation under award DMR-1807810 (time-resolved spectroscopy), the Center for Emergent Materials, an NSF MRSEC under award no. DMR-1420451 (bulk CrI3 crystal growth and device fabrication) and the Air Force Office of Scientific Research under award no. FA9550-19-1-0390 (data analysis). This work was also partially supported by the Cornell Center for Materials Research with funding from the NSF MRSEC program under DMR-1719875 (optical characterization). D.W. acknowledges financial support by the German Science Foundation (Deutsche Forschungsgemeinschaft, DFG) under fellowship no. WE6480/1. X.-X.Z. acknowledges a Postdoctoral Fellowship from the Kavli Institute at Cornell (KIC). K.F.M. acknowledges support from the David and Lucille Packard Fellowship.

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X.-X.Z., K.F.M. and J.S. designed the study. X.-X.Z. developed the time-resolved spectroscopy set-up and performed the measurements. L.L. fabricated the devices and assisted X.X.-Z. in the measurements. D.W. and J.G. grew the bulk CrI3 crystals. X.-X.Z., K.F.M. and J.S. co-wrote the manuscript. All the authors discussed the results and commented on the manuscript.

Corresponding authors

Correspondence to Kin Fai Mak or Jie Shan.

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Supplementary Information

Supplementary Data and Figs. 1–12.

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Zhang, XX., Li, L., Weber, D. et al. Gate-tunable spin waves in antiferromagnetic atomic bilayers. Nat. Mater. 19, 838–842 (2020). https://doi.org/10.1038/s41563-020-0713-9

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