Field-resolved observation of exciton coherence in a van der Waals magnet

Nature Materials (2026)Cite this article The emergence of coherence among electronic quasiparticles underlies collective quantum phenomena from superconductivity to superradiance. In semiconductors, exciton coherence is generally thought to decay rapidly due to scattering and dephasing, limiting its persistence on ultrafast timescales. Here we demonstrate a light-field-driven mechanism that creates and stabilizes exciton coherence in the layered antiferromagnet CrSBr. We directly record the coherent optical field emitted by excitons and track in real time how a deterministic phase, imprinted by the excitation laser, drives incoherent excitons to synchronize into a collective state. This ensemble remains phase coherent for more than 2 ps, whereas its resonance energy undergoes an ultrafast modulation mediated by spin and lattice interactions. The time-resolved field evolution indicates that the multiple peaks seen in conventional spectra originate from a single excitonic resonance subject to dynamic energy modulation. Our findings establish optical phase imprinting as a mechanism to control and sustain collective order in semiconducting magnets, bridging light-driven dynamics with excitonic and magnetic correlations in layered quantum 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 checkoutSource data are provided with this paper.The codes used to generate the data for this study are available from the corresponding authors upon request.Strogatz, S. H. From Kuramoto to Crawford: exploring the onset of synchronization in populations of coupled oscillators. Phys. D 143, 1–20 (2000).Article Google Scholar Bardeen, J., Cooper, L. N. & Schrieffer, J. R. Theory of superconductivity. Phys. Rev. 108, 1175–1204 (1957).Article CAS Google Scholar van Delft, D. & Kes, P. The discovery of superconductivity. Phys. Today 63, 38–43 (2010).Article Google Scholar Anderson, M. H., Ensher, J. R., Matthews, M. R., Wieman, C. E. & Cornell, E. A. Observation of Bose-Einstein condensation in a dilute atomic vapor. Science 269, 198–201 (1995).Article CAS PubMed Google Scholar Dicke, R. H. Coherence in spontaneous radiation processes. Phys. Rev. 93, 99–110 (1954).Article CAS Google Scholar Burnham, D. C. & Chiao, R. Y. Coherent resonance fluorescence excited by short light pulses. Phys. Rev. 188, 667–675 (1969).Article CAS Google Scholar Bonifacio, R. & Lugiato, L. A. Cooperative radiation processes in two-level systems: superfluorescence. Phys. Rev. A 11, 1507–1521 (1975).Article Google Scholar Heinzen, D. J., Thomas, J. E. & Feld, M. S. Coherent ringing in superfluorescence. Phys. Rev. Lett. 54, 677–680 (1985).Article CAS PubMed Google Scholar Rainò, G. et al. Superfluorescence from lead halide perovskite quantum dot superlattices. Nature 563, 671–675 (2018).Article PubMed Google Scholar Biliroglu, M. et al. Unconventional solitonic high-temperature superfluorescence from perovskites. Nature 642, 71–77 (2025).Article CAS PubMed Google Scholar Mueller, T. & Malic, E. Exciton physics and device application of two-dimensional transition metal dichalcogenide semiconductors. npj 2D Mater. Appl. 2, 29 (2018).Article Google Scholar Selig, M. et al. Dark and bright exciton formation, thermalization, and photoluminescence in monolayer transition metal dichalcogenides. 2D Mater. 5, 035017 (2018).Article Google Scholar Jakubczyk, T. et al. Radiatively limited dephasing and exciton dynamics in MoSe2 monolayers revealed with four-wave mixing microscopy. Nano Lett. 16, 5333–5339 (2016).Article CAS PubMed PubMed Central Google Scholar Martin, E. W. et al. Encapsulation narrows and preserves the excitonic homogeneous linewidth of exfoliated monolayer MoSe2. Phys. Rev. Appl.14, 021002 (2020).Article CAS Google Scholar Siday, T. et al. Ultrafast nanoscopy of high-density exciton phases in WSe2. Nano Lett. 22, 2561–2568 (2022).Article CAS PubMed Google Scholar Meineke, C. et al. Ultrafast exciton dynamics in the atomically thin van der Waals magnet CrSBr. Nano Lett. 24, 4101–4107 (2024).Article CAS PubMed PubMed Central Google Scholar Steinleitner, P. et al. Direct observation of ultrafast exciton formation in a monolayer of WSe2. Nano Lett. 17, 1455–1460 (2017).Article CAS PubMed Google Scholar Merkl, P. et al. Ultrafast transition between exciton phases in van der Waals heterostructures. Nat. Mater. 18, 691–696 (2019).Article CAS PubMed Google Scholar Liebich, M. et al. Controlling Coulomb correlations and fine structure of quasi-one-dimensional excitons by magnetic order. Nat. Mater. 24, 384–390 (2025).Article CAS PubMed PubMed Central Google Scholar Cundiff, S. T. Coherent spectroscopy of semiconductors. Opt. Express 16, 4639–4664 (2008).Article PubMed Google Scholar Rather, S. R., Weingartz, N. P., Kromer, S., Castellano, F. N. & Chen, L. X. Spin–vibronic coherence drives singlet–triplet conversion. Nature 620, 776–781 (2023).Article PubMed Google Scholar Timmer, D. et al. Ultrafast coherent exciton couplings and many-body interactions in monolayer WS2. Nano Lett. 24, 8117–8125 (2024).Article CAS PubMed PubMed Central Google Scholar Schiffrin, A. et al. Optical-field-induced current in dielectrics. Nature 493, 70–74 (2013).Article PubMed Google Scholar Schultze, M. et al. Controlling dielectrics with the electric field of light. Nature 493, 75–78 (2013).Article PubMed Google Scholar Keiber, S. et al. Electro-optic sampling of near-infrared waveforms. Nat. Photon. 10, 159–162 (2016).Article CAS Google Scholar Park, S. B. et al. Direct sampling of a light wave in air. Optica 5, 402–408 (2018).Article Google Scholar Bionta, M. R. et al. On-chip sampling of optical fields with attosecond resolution. Nat. Photon. 15, 456–460 (2021).Article CAS Google Scholar Liu, Y., Beetar, J. E., Nesper, J., Gholam-Mirzaei, S. & Chini, M. Single-shot measurement of few-cycle optical waveforms on a chip. Nat. Photon. 16, 109–112 (2022).Article CAS Google Scholar Ridente, E. et al. Electro-optic characterization of synthesized infrared-visible light fields. Nat. Commun. 13, 1111 (2022).Article CAS PubMed PubMed Central Google Scholar Blöchl, J. et al. Spatiotemporal sampling of near-petahertz vortex fields. Optica 9, 755–761 (2022).Article Google Scholar Altwaijry, N. et al. Broadband photoconductive sampling in gallium phosphide. Adv. Opt. Mater. 11, 2202994 (2023).Article CAS Google Scholar Yeung, M. et al. Lightwave-electronic harmonic frequency mixing. Sci. Adv.10, eadq0642 (2024).Article CAS PubMed PubMed Central Google Scholar Srivastava, A. et al. Near-petahertz fieldoscopy of liquid. Nat. Photon. 18, 1320–1326 (2024).Article CAS Google Scholar Yeung, M. et al. Bandwidth of lightwave-driven electronic response from metallic nanoantennas. Nano Lett. 25, 5250–5257 (2025).Article CAS PubMed Google Scholar Heinzerling, A. M. et al. Field-resolved attosecond solitons. Nat. Photon. 19, 772–777 (2025).Article CAS Google Scholar Telford, E. J. et al. Layered antiferromagnetism induces large negative magnetoresistance in the van der Waals semiconductor CrSBr. Adv. Mater. 32, 2003240 (2020).Article CAS Google Scholar Lin, K. et al. Strong exciton–phonon coupling as a fingerprint of magnetic ordering in van der Waals layered CrSBr. ACS Nano 18, 2898–2905 (2024).Article CAS PubMed PubMed Central Google Scholar Wilson, N. P. et al. Interlayer electronic coupling on demand in a 2D magnetic semiconductor. Nat. Mater. 20, 1657–1662 (2021).Article CAS PubMed Google Scholar Bae, Y. J. et al. Exciton-coupled coherent magnons in a 2D semiconductor. Nature 609, 282–286 (2022).Article CAS PubMed Google Scholar Marques-Moros, F., Boix-Constant, C., Mañas-Valero, S., Canet-Ferrer, J. & Coronado, E. Interplay between optical emission and magnetism in the van der Waals magnetic semiconductor CrSBr in the two-dimensional limit. ACS Nano 17, 13224–13231 (2023).Article CAS PubMed PubMed Central Google Scholar Shao, Y. et al. Magnetically confined surface and bulk excitons in a layered antiferromagnet. Nat. Mater. 24, 391–398 (2025).Article CAS PubMed Google Scholar Dirnberger, F. et al. Magneto-optics in a van der Waals magnet tuned by self-hybridized polaritons. Nature 620, 533–537 (2023).Article CAS PubMed Google Scholar Li, C. et al. 2D CrSBr enables magnetically controllable exciton-polaritons in an open cavity. Adv. Funct. Mater. 34, 2411589 (2024).Article CAS Google Scholar Ziebel, M. E. et al. CrSBr: an air-stable, two-dimensional magnetic semiconductor. Nano Lett. 24, 4319–4329 (2024).Article CAS PubMed Google Scholar Datta, B. et al. Magnon-mediated exciton–exciton interaction in a van der Waals antiferromagnet. Nat. Mater. 24, 1027–1033 (2025).Smolenski, S. et al. Large exciton binding energy in a bulk van der Waals magnet from quasi-1D electronic localization. Nat. Commun. 16, 1134 (2025).Article CAS PubMed PubMed Central Google Scholar Yeung, M.

Lightwave Electronics Based on Nanoantenna Networks. PhD thesis, Massachusetts Institute of Technology (2024).Göser, O., Paul, W. & Kahle, H. G. Magnetic properties of CrSBr. J. Magn. Magn. Mater. 92, 129–136 (1990).Article Google Scholar Klein, J. et al. The bulk van der Waals layered magnet CrSBr is a quasi-1D material. ACS Nano 17, 5316–5328 (2023).Article CAS PubMed Google Scholar López-Paz, S. A. et al. Dynamic magnetic crossover at the origin of the hidden-order in van der Waals antiferromagnet CrSBr. Nat. Commun. 13, 4745 (2022).Article PubMed PubMed Central Google Scholar Adak, P. C. et al. Directional flow of confined polaritons in CrSBr. Adv. Mater. 37, e12557 (2025).Ritzkowsky, F. et al. High-repetition-rate CEP-stable 2 μm optical parametric amplifier. J. Opt. Soc. Am. B 43, 207–212 (2026).Article CAS Google Scholar Scheie, A. et al. Spin waves in the magnetic semiconductor CrSBr. Adv. Sci. 25, 2202467 (2022).Article Google Scholar Perdew, J. P., Burke, K. & Ernzerhof, M. Generalized gradient approximation made simple. Phys. Rev. Lett. 77, 3865–3868 (1996).Article CAS PubMed Google Scholar Giannozzi, P. et al. QUANTUM ESPRESSO: a modular and open-source software project for quantum simulations of materials. J. Phys. Condens. Matter 21, 395502 (2009).Article PubMed Google Scholar Deslippe, J. et al. BerkeleyGW: a massively parallel computer package for the calculation of the quasiparticle and optical properties of materials and nanostructures. Comput. Phys. Commun. 183, 1269–1289 (2012).Article CAS Google Scholar Hybertsen, M. S. & Louie, S. G. Electron correlation in semiconductors and insulators: band gaps and quasiparticle energies. Phys. Rev. B 34, 5390–5413 (1986).Article CAS Google Scholar Rohlfing, M. & Louie, S. G. Electron-hole excitations and optical spectra from first principles. Phys. Rev. B 62, 4927–4944 (2000).Article CAS Google Scholar Tabataba-Vakili, F. et al. Doping-control of excitons and magnetism in CrSBr. Nat. Commun. 15, 4735 (2024).Article CAS PubMed PubMed Central Google Scholar Download referencesWe acknowledge support from the US Department of Energy, Materials Science and Engineering Division, Office of Basic Energy Sciences (BES DMSE) (analysis and manuscript writing) and the EPiQS Initiative grant (GBMF9459) (Instrumentation). The lightwave sampling devices used in this work were supported by the Air Force Office of Scientific Research under award number FA9550-18-1-0436, and fabrication was carried out through the use of MIT.nano. The modelling and theory work were supported in part by the European Research Council (ERC-2024-SyG-101167294; UnMySt), the Cluster of Excellence: Advanced Imaging of Matter (AIM), and Grupos Consolidados UPV/EHU (IT1249-19). We also acknowledge support from the Max Planck-New York City Center for Non-Equilibrium Quantum Phenomena.

The Flatiron Institute is a division of the Simons Foundation. Synthetic work at Columbia University was supported by the Materials Science and Engineering Research Center (MRSEC) on Precision Assembly of Quantum Materials (PAQM) through NSF award DMR-2011738 and the US Army Research Office under grant number W911NF-23-1-0056. M.Y. acknowledges support from the National Science Foundation MPS-Ascend Postdoctoral Research Fellowship under grant number 2402151. A.v.H., C.H. and F.R. acknowledge support from the Alexander von Humboldt Foundation for the financial support from the Feodor Lynen Research Fellowship. E.V.B. acknowledges funding from the European Union’s Horizon Europe research and innovation programme under the Marie Skłodowska-Curie grant agreement number 101106809. F.Z. acknowledges support from the Alexander von Humboldt Foundation for the financial support from the Humboldt Research Fellowship. G.L.D. acknowledges support from the Progetto Rocca Postdoctoral Fellowship. C.H. acknowledges support from the US Department of Energy, Office of Science, Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division, through the AMOS program. F.R., P.D.K. and laser development were supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, under award number DE-SC0024173. We thank J. Niroula for their help in measuring the CrSBr flake using Dektak. We thank T. Heinz and M. Baldo for fruitful discussions pertaining to the field-resolved measurements. We are grateful to M. Meierhofer, J. Pettine and M. Buzzi for providing valuable feedback, and B. Mazur and M. Sere for reading the manuscript.Massachusetts Institute of Technology, Cambridge, MA, USAMatthew Yeung, Alexander von Hoegen, Felix Ritzkowsky, Jack B. Maier, Gian Luca Dolso, Christian Heide, Karl K. Berggren, Phillip D. Keathley & Nuh GedikMax Planck Institute for the Structure and Dynamics of Matter, Hamburg, DE, GermanyEmil Viñas Boström, Fangzhou Zhao & Angel RubioStanford PULSE Institute, Menlo Park, CA, USAChristian HeideUniversity of Central Florida, Orlando, FL, USAChristian HeideColumbia University, New York, NY, USADaniel G. Chica & Xavier RoyThe Flatiron Institute, New York, NY, USAAngel RubioSearch 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 ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarM.Y., A.v.H. and N.G. conceived the study of exciton dynamics in CrSBr. M.Y. built the experimental measurement setup. M.Y. performed the field-resolved measurements with support from F.R., C.H., A.v.H. and G.L.D. M.Y. analysed the experimental data with input from A.v.H., E.V.B. and F.Z. J.B.M. performed the pump–probe and reflectance measurements with input from A.v.H. and M.Y. E.V.B., F.Z. and A.R. performed the first-principles calculations and modelling. The crystals were grown by D.G.C. under the supervision of X.R. M.Y. wrote the first draft of the manuscript with input from all authors. M.Y. fabricated the lightwave sampling devices used to perform the field-resolved spectroscopy experiments under the supervision of K.K.B. and P.D.K. The OPA was built by M.Y. and F.R., with support from G.L.D. and supervised by P.D.K. The project was supervised and coordinated by N.G.Correspondence to Phillip D. Keathley or Nuh Gedik.F.R., K.K.B. and P.D.K. acknowledge the patent ‘Integrated optical field sampling platform’ (US12287239B2). The remaining authors declare no competing interests.Nature Materials thanks Hanieh Fattahi 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.Supplementary Figs. 1–26 and Discussion.Source data (first column is time and the other columns are the measured electric field).Source data for the pump–probe data.Source data for the pump–probe imaging maps.Source data (first column is time and the other columns are the measured electric field).Source data (first column is time and the other columns are the measured electric field).Columns are the electric field data used for all of the experimental figures in the main text with the first column being time; the decay times are shown.Columns are the electric field data used for all of the experimental figures in the main text with the first column being time; experimental intensity spectrum and experimental STFT intensity spectrum data are also shown.Calculated absorption spectrum and experimental intensity spectrum.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 permissionsYeung, M., von Hoegen, A., Viñas Boström, E. et al. Field-resolved observation of exciton coherence in a van der Waals magnet. Nat. Mater. (2026). https://doi.org/10.1038/s41563-026-02598-3Download citationReceived: 29 October 2025Accepted: 01 April 2026Published: 01 May 2026Version of record: 01 May 2026DOI: https://doi.org/10.1038/s41563-026-02598-3Anyone 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