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Observation of a hidden charge density wave liquid

Nature Physics volume 22, pages 68–74 (2026)Cite this article

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Abstract

Charge density waves, electronic crystals that form within a host solid, have long been theorized to melt into a spatially textured electronic liquid. Although such liquid charge density waves have not been previously observed, they may be central to the phase diagrams of correlated electron systems, including high-temperature superconductors and quantum Hall states. In 1T-TaS2, a promising material for hosting a liquid charge density wave, a structural phase transition hinders observation. Here we use femtosecond light pulses to bypass this transition, revealing how topological defect dynamics govern hidden charge density wave correlations. Following photoexcitation, charge density wave diffraction peaks broaden azimuthally, indicating the emergence of a hexatic state. At elevated temperatures, photoexcitation fully destroys both translational and orientational orders, leaving only a ring of diffuse scattering—the hallmark of a liquid charge density wave. These findings offer compelling evidence for a defect-unbinding transition to a charge density wave liquid. More broadly, this approach demonstrates a route to uncover electronic phases obscured by intervening transitions in thermal equilibrium.

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Fig. 1: Defect-mediated melting of a 2D triangular lattice.
Fig. 2: Emergence of hexatic and liquid CDW states following a light-induced suppression of the equilibrium order.
Fig. 3: Evolution of solid, hexatic and liquid CDW states in the quasi-thermal regime.
Fig. 4: Molecular dynamics simulation of a solid–liquid–hexatic transition with quenched interaction strength.

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Data availability

The data that support the findings of this study are provided in the Article. Source data are provided with this paper. These data are also available via Zenodo at https://doi.org/10.5281/zenodo.15453892 (ref. 56). Additional data related to the paper are available from the corresponding author upon request.

Code availability

The code used to produce the figures in this work is available via Zenodo at https://doi.org/10.5281/zenodo.17383782 (ref. 57).

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Acknowledgements

We thank S. E. Brown, R. Bruinsma and X. Zhang for insightful discussions regarding this work. We thank M. Rasiah, S. Wang, J. Higgins, A. Ody and A. Kulkarni for their instrumentation work in the kiloelectronvolt UED setup at University of California, Los Angeles. We acknowledge support from the US Department of Energy, Office of Science, Office of Basic Energy Sciences, under award number DE-SC0023017 (A.K.; data taking, data analysis and manuscript writing). We also acknowledge support from STROBE: a National Science Foundation Science and Technology Center under grant number DMR-1548924 (A.K. and P.M.; instrumentation).

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Author notes

  1. These authors contributed equally: Joshua S. H. Lee, Thomas M. Sutter.

Authors and Affiliations

  1. Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, CA, USA

    Joshua S. H. Lee, Thomas M. Sutter, Pietro Musumeci & Anshul Kogar

  2. Department of Physics, Drexel University, Philadelphia, PA, USA

    Goran Karapetrov

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  1. Joshua S. H. Lee
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Contributions

J.S.H.L. and T.M.S. performed the diffraction measurements. J.S.H.L. and T.M.S. prepared the samples for measurements. J.S.H.L. and T.M.S. built the kiloelectronvolt UED beamline at University of California, Los Angeles, under the supervision of A.K. and P.M. G.K. grew the crystals for the experiment. J.S.H.L. performed the data analysis with theoretical input from T.M.S. and A.K. T.M.S. performed the molecular dynamics simulations. J.S.H.L., T.M.S. and A.K. wrote the paper with important input from all other authors. The work was supervised by A.K.

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Correspondence to Anshul Kogar.

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Nature Physics thanks Haiyun Liu, Chih-Wei Luo and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary information

Supplementary Information

Supplementary Notes I–XIV, Figs. 1–12 and references.

Supplementary Video 1

Animated version of Fig. 2e,j, but for all times t rather than only at selected times. The dynamics at the initial temperatures of 360 K and 520 K are animated side by side for comparison.

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Statistical source data.

Source Data Fig. 2

Statistical source data.

Source Data Fig. 3

Statistical source data.

Source Data Fig. 4

Statistical source data.

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Lee, J.S.H., Sutter, T.M., Karapetrov, G. et al. Observation of a hidden charge density wave liquid. Nat. Phys. 22, 68–74 (2026). https://doi.org/10.1038/s41567-025-03108-z

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