Evidence of time-reversal symmetry breaking above the charge density wave order in a kagome metal

Nature Physics (2026) Cite this article Spontaneous symmetry breaking in kagome metals remains highly debated, especially with respect to the presence of time-reversal symmetry breaking and the temperature range over which it develops. A loop-current order, characterized by complex phases in intersite hopping, has been proposed as the mechanism responsible for the breaking of time-reversal symmetry, although it has not yet been confirmed experimentally. Here we present evidence that time-reversal symmetry is broken well above the temperature at which the charge density wave order develops in the kagome metal CsV3Sb5. Using momentum-resolved and domain-selective measurements of circular dichroism in photoemission intensity, we observe dichroic signal that originates from the time-reversal symmetry broken state. This finding also points to the presence of loop-current order. The temperature dependence of the dichroic response shows a complex evolution, revealing how loop-current order is intertwined with the charge ordered state. Our results, therefore, not only support the existence of loop-current order in this compound but also highlight a hierarchy of phase transitions—from loop-current order to charge density wave order and ultimately to superconductivity. These insights deepen our understanding of the phase landscape in kagome metals and highlight connections with a correlated system exhibiting analogous transition hierarchy.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 findings of this work are available from the corresponding authors upon reasonable request. Source data are provided with this paper.The band structure calculations used in this work are available from the corresponding authors upon reasonable request.Ye, L. et al. Hopping frustration-induced flat band and strange metallicity in a kagome metal. Nat. Phys. 20, 610–614 (2024).Article Google Scholar Ortiz, B. R. et al. CsV3Sb5: a Z2 topological kagome metal with a superconducting ground state. Phys. Rev. Lett. 125, 247002 (2020).Article ADS Google Scholar Hu, Y. et al. Topological surface states and flat bands in the kagome superconductor CsV3Sb5. Sci. Bull. 67, 495–500 (2022).Article Google Scholar Yin, J.-X., Lian, B. & Hasan, M. Z. Topological kagome magnets and superconductors. Nature 612, 647–657 (2022).Article ADS Google Scholar Wu, X. et al. Nature of unconventional pairing in the kagome superconductors AV3Sb5 (A = K, Rb, Cs). Phys. Rev. Lett. 127, 177001 (2021).Article ADS Google Scholar Hu, Y. et al. Rich nature of Van Hove singularities in kagome superconductor CsV3Sb5. Nat. Commun. 13, 2220 (2022).Article ADS Google Scholar Liu, G. et al. Observation of anomalous amplitude modes in the kagome metal CsV3Sb5. Nat. Commun. 13, 3461 (2022).Article ADS Google Scholar Li, H. et al. Discovery of conjoined charge density waves in the kagome superconductor CsV3Sb5. Nat. Commun. 13, 6348 (2022).Article ADS Google Scholar Zhong, Y. et al. Nodeless electron pairing in CsV3Sb5-derived kagome superconductors. Nature 617, 488–492 (2023).Article ADS Google Scholar Kang, M. et al. Charge order landscape and competition with superconductivity in kagome metals. Nat. Mater. 22, 186–193 (2023).

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Gaulin for helpful discussions.J.C., G.L., J.H., C.-y.L., Y.A., S.G. and Y.K. acknowledge support from the National Research Foundation of Korea (NRF) grant funded by the Ministry of Science and ICT of the government of South Korea (MSIT) under grant numbers RS-2022-NR066723, RS-2022-00143178, RS-2024-00345856 and KRISS-GP2025-0015. S.L. acknowledges support from NRF grants funded by MSIT under grant numbers 2021R1A2C1093060 and RS-2023-00281839, and from the Air Force Office of Scientific Research under award number FA23862514054. M.J.H. acknowledges support from NRF grants funded by MSIT under grant numbers RS-2025-00559042 and RS-2025-02243032. Y.S., K.-T.K. and K.H.K. acknowledge support from NRF grants funded by MSIT under grant numbers RS-2023-00220471 and RS-2024-00338707. Use of the Advanced Light Source (ALS) was supported by the Office of Basic Energy Sciences of the US Department of Energy under contract number DE-AC02-05CH11231.Jounghoon HyunPresent address: Department of Physics and Astronomy, Rice University, Houston, TX, USAThese authors contributed equally: Jaehun Cha, Hyunggeun Lee, Sangjun Sim.Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon, Republic of KoreaJaehun Cha, Hyunggeun Lee, Sangjun Sim, Jae-Ho Han, Gyubin Lee, Jounghoon Hyun, Yeojin Ahn, Seonggeon Gim, SungBin Lee, Myung Joon Han & Yeongkwan KimCenter for Novel States of Complex Materials Research, Department of Physics and Astronomy, Seoul National University, Seoul, Republic of KoreaYeahan Sur, Kwang-Tak Kim & Kee Hoon KimDepartment of Materials Science and Metallurgy, University of Cambridge, Cambridge, UKSun-Woo KimDonostia International Physics Center, San Sebastián, SpainChan-young LimAdvanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, USAJonathan D. DenlingerDepartment of Physics, Ajou University, Suwon, Republic of KoreaSunghun KimInstitute of Applied Physics, Seoul National University, Seoul, Republic of KoreaKee Hoon KimSearch 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 ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarY.K., M.J.H. and S.L. conceived the idea and supervised the project. Y.S., K.-T.K. and K.H.K. synthesized the CsV3Sb5 single crystals. J.C., G.L., J.H., C.-y.L., Y.A., S.G., S.K. and Y.K. performed the CD-ARPES measurements with support from Y.K. and J.D.D. J.C. and Y.K. analysed the CD-ARPES data. H.L., S.S., S.-W.K. and M.J.H. carried out the density functional theory and tight-binding calculations of OAM. J.-H.H. and S.L. developed the theoretical model of charge loop current and bond ordering. All authors discussed the results. Y.K., M.J.H. and S.L. co-wrote the paper with contributions from all authors.Correspondence to SungBin Lee, Myung Joon Han or Yeongkwan Kim.The authors declare no competing interests.Nature Physics thanks Jiangping Hu and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.Supplementary Figs. 1–18.Numerical source data for Fig. 1b,c.Numerical source data for Fig. 2c,d.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 permissionsCha, J., Lee, H., Sim, S. et al. Evidence of time-reversal symmetry breaking above the charge density wave order in a kagome metal. Nat. Phys. (2026). https://doi.org/10.1038/s41567-026-03331-2Download citationReceived: 24 June 2025Accepted: 11 May 2026Published: 15 June 2026Version of record: 15 June 2026DOI: https://doi.org/10.1038/s41567-026-03331-2Anyone 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