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Terahertz emission from giant optical rectification in a van der Waals material

Nature Materials volume 24, pages 1203–1208 (2025)Cite this article

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Abstract

The exfoliation and stacking of two-dimensional van der Waals crystals have created unprecedented opportunities in the discovery of quantum phases. A major obstacle to the advancement of this field is the limited spectroscopic access due to a mismatch in the sample sizes (10−6–10−5 m) and the wavelengths (10−4–10−3 m) of electromagnetic radiation relevant to their low-energy excitations. Here we introduce ferroelectric semiconductor NbOI2 as a two-dimensional van der Waals material capable of operating as a van der Waals terahertz emitter. We demonstrate intense and broadband terahertz generation from NbOI2 with an optical rectification efficiency that is more than one order of magnitude higher than that of ZnTe, the current standard terahertz emitter. Moreover, this NbOI2 terahertz emitter can be integrated into van der Waals heterostructures to enable on-chip near-field terahertz spectroscopy of a target van der Waals material and device. Our approach provides a general spectroscopic tool for two-dimensional van der Waals materials and quantum matter.

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Fig. 1: Near-field THz spectroscopy exploiting efficient THz emission of 2D vdW ferroelectric NbOI2.
Fig. 2: Thickness dependence of THz emission.
Fig. 3: In situ and near-field THz-TDS in a vdW structure.

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Data availability

The data that support the findings of this study are presented in the article and its Supplementary Information. Further data are available from the corresponding author upon reasonable request.

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Acknowledgements

Experiments on the discovery of THz emission (Fig. 1) and implementation in near-field microscopy and spectroscopy (Fig. 3), as well as sample synthesis and characterization, were supported by the Materials Science and Engineering Research Center (MRSEC) through National Science Foundation (NSF) grant DMR-2011738. Experiments on thickness dependence and THz emission mechanisms (Fig. 2) were supported by the US Army Research Office, grant number W911NF-23-1-0056. J.W.M. acknowledges support by Programmable Quantum Materials, an Energy Frontier Research Center funded by the US Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES), under award DE-SC0019443. X.Z. acknowledges support by the Max Planck – New York City Center for Non-Equilibrium Quantum Phenomena for fruitful collaborations, interactions and discussions with the Max Planck Institutes (MPIs), particularly M. Bonn of MPI-Mainz, and M. Fechner and H. M. Bretscher of MPI-Hamburg. T.H. acknowledges support by the Japan Society for the Promotion of Science (JSPS) Overseas Postdoctoral Research Fellowship programme. C.-Y.H. acknowledges support from the Taiwan–Columbia scholarship funded by the Ministry of Education of Taiwan and Columbia University.

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Authors and Affiliations

  1. Department of Chemistry, Columbia University, New York, NY, USA

    Taketo Handa, Chun-Ying Huang, Yiliu Li, Nicholas Olsen, Daniel G. Chica, David D. Xu, Xavier Roy & Xiaoyang Zhu

  2. Department of Physics, Columbia University, New York, NY, USA

    Felix Sturm & James W. McIver

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  1. Taketo Handa
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Contributions

T.H. and X.Z. conceived this work. T.H. and C.-Y.H. carried out the optical measurements. C.-Y.H., N.O. and F.S. prepared the exfoliated samples under the supervision of X.Z. and J.W.M.; Y.L. and D.D.X. fabricated the vdW heterostructures. D.G.C. synthesized the crystals under the supervision of X.R.; X.Z. supervised the project. The paper was prepared by T.H. and X.Z. in consultation with all other authors. All authors read and commented on the paper.

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Correspondence to Xiaoyang Zhu.

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Nature Materials thanks Su-Yang Xu and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary Figs. 1–15, Notes 1–10 and References.

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Handa, T., Huang, CY., Li, Y. et al. Terahertz emission from giant optical rectification in a van der Waals material. Nat. Mater. 24, 1203–1208 (2025). https://doi.org/10.1038/s41563-025-02201-1

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