Observation of Floquet-induced gap in graphene

Nature Materials (2026)Cite this article Floquet engineering provides a powerful pathway for creating non-equilibrium phases of matter with tailored electronic structures and properties through time-periodic driving. As the original theoretical prototype, graphene established the framework in which the Floquet topological insulator with the light-induced anomalous Hall effect was proposed. However, the defining spectroscopic signature of Floquet engineering in graphene, light-induced hybridization (avoided-crossing) gap at Floquet band crossings, has remained experimentally elusive. Here we report the direct observation of a Floquet-induced hybridization gap in monolayer graphene under resonant driving by a strong light field. Time- and angle-resolved photoemission spectroscopy reveals a gap opening at Floquet band crossings, accompanied by coherent Floquet sidebands. The gap exhibits pronounced momentum anisotropy, featuring two Dirac nodes protected by spatiotemporal symmetry and tunable by light polarization. These results provide the long-sought experimental demonstration of Floquet band engineering in graphene, opening up opportunities for light-field-engineered quantum phases in graphene and related materials.This is a preview of subscription content, access via your institution Access Nature and 54 other Nature Portfolio journals Get Nature+, our best-value online-access subscription $32.99 / 30 days cancel any timeSubscribe to this journal Receive 12 print issues and online access $259.00 per yearonly $21.58 per issueBuy this articleUSD 39.95Prices may be subject to local taxes which are calculated during checkoutAll data supporting the results of this study are available within the Article. Additional data are available from the corresponding author upon request. Source data are provided with this paper.Ashcroft, N. W. & Mermin, N. D.

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Mater. 7, 044201 (2023).Article Google Scholar Download referencesThis work is supported by the National Natural Science Foundation of China (grant numbers 12421004 and 12234011), Tsinghua University Initiative Scientific Research Program (grant number 20251080106), National Key R&D Program of China (grant number 2021YFA1400100), the National Natural Science Foundation of China (grant numbers 12327805, 52388201) and New Cornerstone Science Foundation through the XPLORER PRIZE.These authors contributed equally: Fei Wang, Xuanxi Cai.Department of Physics, Tsinghua University, Beijing, People’s Republic of ChinaFei Wang, Xuanxi Cai, Xiao Tang, Jinxi Lu, Wanying Chen, Tianshuang Sheng, Runfa Feng, Haoyuan Zhong, Hongyun Zhang, Pu Yu & Shuyun ZhouState Key Laboratory of Low-Dimensional Quantum Physics, Tsinghua University, Beijing, People’s Republic of ChinaFei Wang, Xuanxi Cai, Xiao Tang, Jinxi Lu, Wanying Chen, Tianshuang Sheng, Runfa Feng, Haoyuan Zhong, Hongyun Zhang, Pu Yu & Shuyun ZhouFrontier Science Center for Quantum Information, Beijing, People’s Republic of ChinaPu Yu & Shuyun ZhouSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarS.Z. conceived the research project. F.W. and X.C. performed the TrARPES measurements and analysed the data. R.F., X.T. and W.C. prepared the samples. X.C. and H. Zhong developed and optimized the HHG light source. F.W., X.C., J.L., T.S., H. Zhong, H. Zhang and P.Y. discussed the results. F.W., X.C. and S.Z. wrote the manuscript and all authors commented on the manuscript.Correspondence to Shuyun Zhou.The authors declare no competing interests.Nature Materials thanks Stefan Mathias, Michael Sentef and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Peer reviewer reports are available.Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.a, Dispersion image measured before pumping. b, Extracted EDCs within the region marked by the red box and fitting using Fermi-Dirac distribution (red curve), from which EF is extracted. c, Dispersion image measured upon pumping. d, EDCs cut through black box at different delay times with fitting peaks appended.a, Schematic for the experimental geometry. The pump is incident on the monolayer graphene sample at near normal angle, therefore, electric fields for both p-pol. and s-pol. are dominantly confined within the sample plane, and there is negligible out-of-plane light field. b, Schematic illustration of the polarization with respect to the Dirac cone. The light field is along the kx (ky) direction for p-pol. (s-pol.) pump.a-e, Dispersion images measured before pumping (a) and at Δt = 0 fs upon driving at 490 meV with different pump fluence (b-e). f-j, EDCs for data shown in (a-e) at momentum of resonant points. k, Extracted Floquet-induced hybridization gap as a function of the pump fluence. Data in k are presented as fitting values at different pump fluence, with error bars representing the combination of statistical fitting error and estimated systematic contribution.a, A schematic for the resonance points upon driving with different pump photon energies. b, TrARPES dispersion images measured at Δt = -300 fs. c, TrARPES dispersion images measured at Δt = 0 fs upon 490 meV pumping. The pump polarization is along the kx direction and the pump fluence is 4.1 mJ/cm2. d, TrARPES dispersion images measured at Δt = 0 fs upon 600 meV pumping. The pump polarization is along the kx direction and the pump fluence is 6.4 mJ/cm2. e, EDCs for data shown in (b-d) at momentum resonance point.a, A schematic of the experimental geometry for the p-pol. and s-pol. pumps. b-d, TrARPES dispersion images measured at Δt = -300 fs (b) and Δt = 0 fs with p-pol. pump (c) and s-pol. pump (d). The pump photon energy is 490 meV and the pump fluence is 4.1 mJ/cm2. e, EDCs for data shown in (b-d) at momentum resonance points with fitting peaks appended.a, Dispersion image at Δt = 0, with the momentum integration window marked by lines. b, EDCs obtained by integrating over the indicated momentum range. c, Residuals from the EDC fitting, shown on the same scale as (b).a-c, Dispersion images, where dashed boxes indicate the momentum integration windows used for EDCs shown in (d-f). The values are also labeled on the top of each panel. d-f, Extracted gap values obtained from EDC fittings.a, Dispersion image at Δt = 0 with simulated dispersion overplotted. b, Simulated TrARPES spectrum upon pumping.Supplementary Figs. 1 and 2, Table 1 and Sections 1–3.Statistical source data.Statistical source data.Statistical source data.Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.Reprints and permissionsWang, F., Cai, X., Tang, X. et al. Observation of Floquet-induced gap in graphene. Nat. Mater. (2026). https://doi.org/10.1038/s41563-026-02549-yDownload citationReceived: 04 November 2025Accepted: 16 February 2026Published: 23 March 2026Version of record: 23 March 2026DOI: https://doi.org/10.1038/s41563-026-02549-yAnyone you share the following link with will be able to read this content:Sorry, a shareable link is not currently available for this article. Provided by the Springer Nature SharedIt content-sharing initiative