Abstract
Diamond anvils serve as optical windows in static ultrahigh-pressure experiments, now reaching the terapascal regime. However, they exhibit poorly understood changes in their optical properties under multimegabar pressure. Here, we present broadband absorption measurements (ultraviolet to infrared wavelengths) up to 520 GPa, revealing a pronounced loss of transparency with pressure. Diamond Raman scattering is used to infer the stress profile along the anvils’ axis under the assumption of tetragonal distortion, and crucially at the sample interface. This enables a quantitative analysis of absorption spectra, showing an indirect bandgap narrowing towards the infrared, with metallization projected near 560 GPa sample pressure within our stress model. A universal optical behavior is observed across different anvil geometries, which is consistent with the universality of the Raman edge pressure scale, here refined. These findings help define the spectroscopic operational limits of diamond anvil cells under extreme pressure with important implications for recent claims of hydrogen metallization.
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Source data for all figures are provided with this paper. Raw data and code for this study have been deposited to Zenodo and are accessible with https://doi.org/10.5281/zenodo.18350936 (see ref. 39). Source data are provided with this paper.
References
Bassett, W. A. Diamond anvil cell, 50th birthday. High. Press. Res. 29, 163–186 (2009).
Hilberer, A. et al. Enabling quantum sensing under extreme pressure: nitrogen-vacancy magnetometry up to 130 GPa. Phys. Rev. B 107, L220102 (2023).
Li, B. et al. Diamond anvil cell behavior up to 4 Mbar. Proc. Natl. Acad. Sci. 115, 1713–1717 (2018).
Fratanduono, D. E. et al. Establishing gold and platinum standards to 1 terapascal using shockless compression. Science 372, 1063–1068 (2021).
Lazicki, A. et al. Metastability of diamond ramp-compressed to 2 terapascals. Nature 589, 532–535 (2021).
Dewaele, A., Loubeyre, P., Occelli, F., Marie, O. & Mezouar, M. Toroidal diamond anvil cell for detailed measurements under extreme static pressures. Nat. Commun. 9, 2913 (2018).
Dubrovinskaia, N. et al. Terapascal static pressure generation with ultrahigh yield strength nanodiamond. Sci. Adv. 2, e1600341 (2016).
Ashcroft, N. W. Metallic hydrogen: a high-temperature superconductor? Phys. Rev. Lett. 21, 1748–1749 (1968).
Myung, C. W., Hirshberg, B. & Parrinello, M. Prediction of a supersolid phase in high-pressure deuterium. Phys. Rev. Lett. 128, 045301 (2022).
Babaev, E., Sudbø, A. & Ashcroft, N. W. Observability of a projected new state of matter: a metallic superfluid. Phys. Rev. Lett. 95, 105301 (2005).
Eremets, M. I., Drozdov, A. P., Kong, P. P. & Wang, H. Semimetallic molecular hydrogen at pressure above 350 GPa. Nat. Phys. 15, 1246–1249 (2019).
Loubeyre, P., Occelli, F. & Dumas, P. Synchrotron infrared spectroscopic evidence of the probable transition to metal hydrogen. Nature 577, 631–635 (2020).
Loubeyre, P., Occelli, F. & Dumas, P. Compression of D 2 to 460 GPa and isotopic effects in the path to metal hydrogen. Phys. Rev. Lett. 129, 035501 (2022).
Dias, R. P. & Silvera, I. F. Observation of the Wigner-Huntington transition to metallic hydrogen. Science 355, 715–718 (2017).
Geng, H. Y. Public debate on metallic hydrogen to boost high pressure research. Matter Radiat. Extrem. 2, 275–277 (2017).
Akahama, Y. & Kawamura, H. Pressure calibration of diamond anvil Raman gauge to 310GPa. J. Appl. Phys. 100, 043516 (2006).
Akahama, Y. & Kawamura, H. Pressure calibration of diamond anvil Raman gauge to 410 GPa. J. Phys. Conf. Ser. 215, 012195 (2010).
Eremets, M. I. et al. Universal diamond edge Raman scale to 0.5 terapascal and implications for the metallization of hydrogen. Nat. Commun. 14, 907 (2023).
Mao, H. K. & Hemley, R. J. Optical transitions in diamond at ultrahigh pressures. Nature 351, 721–724 (1991).
Ruoff, A. L., Luo, H. & Vohra, Y. K. The closing diamond anvil optical window in multimegabar research. J. Appl. Phys. 69, 6413–6416 (1991).
Surh, M. P., Louie, S. G. & Cohen, M. L. Band gaps of diamond under anisotropic stress. Phys. Rev. B 45, 8239–8247 (1992).
Onodera, A. et al. Pressure dependence of the optical-absorption edge of diamond. Phys. Rev. B 44, 12176–12179 (1991).
Trojan, I. A., Eremets, M. I., Korolik, M. Y. U., Struzhkin, V. V. & Utjuzh, A. N. Fundamental gap of diamond under hydrostatic pressure. Jpn. J. Appl. Phys. 32, 282 (1993).
Tang, J. et al. Metallization and positive pressure dependency of bandgap in solid neon. J. Chem. Phys. 150, 111103 (2019).
Shen, G. et al. Toward an international practical pressure scale: a proposal for an IPPS ruby gauge (IPPS-Ruby2020). High. Press. Res. 40, 299–314 (2020).
Mohammed Idris Bakhit, A., Mutisya, S. & Scandolo, S. Raman frequencies of diamond under non-hydrostatic pressure. Appl. Phys. Lett. 119, 211902 (2021).
Ruoff, A. L. & Luo, H. Pressure strengthening: a possible route to obtaining 9 Mbar and metallic diamonds. J. Appl. Phys. 70, 2066–2070 (1991).
Akahama, Y. & Kawamura, H. Raman study on the stress state of [111] diamond anvils at multimegabar pressure. J. Appl. Phys. 98, 083523 (2005).
Timoshenko, S. P. & Goodier, J. N. Theory of Elasticity (McGraw-Hill Book Company Inc., 1951).
Lee, S. K. et al. Imaging of the electronic bonding of diamond at pressures up to 2 million atmospheres. Sci. Adv. 9, eadg4159 (2023).
Clark, C., Dean, P. J. & Harris, P. V. Intrinsic edge absorption in diamond. Proc. R. Soc. Lond. Ser. A. Math. Phys. Sci. 277, 312–329 (1964).
Cheng, L., Zhu, S., Ouyang, X. & Zheng, W. Bandgap evolution of diamond. Diam. Relat. Mater. 132, 109638 (2023).
Asaumi, K., Mori, T. & Kondo, Y. Effect of very high pressure on the optical absorption edge in solid Xe and its implication for metallization. Phys. Rev. Lett. 49, 837–840 (1982).
Pascarelli, S. et al. Materials under extreme conditions using large X-ray facilities. Nat. Rev. Methods Prim. 3, 82 (2023).
Ji, C. et al. Ultrahigh-pressure crystallographic passage towards metallic hydrogen. Nature 641, 904–909 (2025).
Goncharov, A. F. & Struzhkin, V. V. Comment on “Observation of the Wigner-Huntington transition to metallic hydrogen”. Science 357, eaam9736 (2017).
Liu, X. D., Dalladay-Simpson, P., Howie, R. T., Li, B. & Gregoryanz, E. Comment on “Observation of the Wigner-Huntington transition to metallic hydrogen”. Science 357, eaan2286 (2017).
Monacelli, L., Casula, M., Nakano, K., Sorella, S. & Mauri, F. Quantum phase diagram of high-pressure hydrogen. Nat. Phys. 19, 845–850 (2023).
Hilberer, A. et al. Source data for: Spectroscopic limits of diamond anvils to 520 GPa and projected bandgap closure. Zenodo https://doi.org/10.5281/zenodo.18350936 (2026).
Acknowledgements
We acknowledge European Synchrotron Radiation Facility (ESRF) access under proposal HC-4884 for X-ray diffraction data on gold and Ne, and we thank M. Mezouar for assistance on the ID27 beamline and for helpful discussions. We acknowledge SOLEIL Synchrotron access under proposal 20241170 and thank F. Jamme for providing access and help with the DISCO UV beamline. We thank G. Geneste for valuable discussions.
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P.L. and P.D. designed the project. P.L. and F.O. prepared the DACs. R.A. FIB-machined the toroidal anvils and gasket holes. P.D. and C.P. performed the UV absorption measurements. P.D. and A.H. performed the visible-IR absorption measurements. G.W., F.O., A.H., and P.L. performed the XRD measurements. A.H. and F.O. performed the Raman measurements. A.H., C.P., P.D., and P.L. analyzed the absorption data. G.W. and A.H. analyzed the XRD data. A.H. and P.L. wrote the draft. All authors discussed the data and revised the manuscript.
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Hilberer, A., Loubeyre, P., Pépin, C. et al. Spectroscopic limits of diamond anvils to 520 GPa and projected bandgap closure. Nat Commun (2026). https://doi.org/10.1038/s41467-026-69533-7
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DOI: https://doi.org/10.1038/s41467-026-69533-7
