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Microscopic origin of excess wings in relaxation spectra of supercooled liquids


Glass formation is encountered in diverse materials. Experiments have revealed that the dynamic relaxation spectra of supercooled liquids generically become asymmetric near the glass transition temperature Tg, where an extended power law emerges at high frequencies. The microscopic origin of this ‘wing’ remains unknown, and has so far been inaccessible to simulations. Here we develop a novel computational approach and study the equilibrium dynamics of model supercooled liquids near Tg. We demonstrate the emergence of a power-law wing in the numerical spectra, which originates from relaxation at rare, localized regions over broadly distributed timescales. We rationalize the asymmetric shape of the relaxation spectra by constructing an empirical model associating heterogeneous activated dynamics with dynamic facilitation, which are the two minimal physical ingredients revealed by our simulations. Our work offers a glimpse into the molecular motion responsible for glass formation at relevant experimental conditions.

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Fig. 1: Emergence of excess wings in a 3D glass former near the glass transition temperature.
Fig. 2: Visualization of spatially heterogeneous and facilitated dynamics.
Fig. 3: Microscopic origin of excess wings.
Fig. 4: Facilitated trap model generically predicts asymmetric winged relaxation spectra.

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Data availability

Source data are provided with this paper. The data that support the findings of this study are available from the corresponding author upon reasonable request.

Code availability

The codes used in this study are available from the corresponding author upon reasonable request.


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We thank G. Biroli, M. Ediger and J. Kurchan for discussions, and S. Nagel for detailed explanations about the experiments. Some simulations were performed at MESO@LR platform at the University of Montpellier. This work was supported by a grant from the Simons Foundation (no. 454933; L.B.), the European Research Council under the EU’s Horizon 2020 programme via grant no. 740269 (C.S.), a Herchel Smith Postdoctoral Research Fellowship (C.S.), a Ramon Jenkins Research Fellowship from Sidney Sussex College, Cambridge (C.S.), and Capital Fund Management - Fondation pour la Recherche (B.G.).

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Authors and Affiliations



B.G., C.S. and L.B. designed the research. B.G. and C.S. carried out the simulations. B.G, C.S. and L.B. analysed the data and wrote the paper.

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Correspondence to Ludovic Berthier.

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Nature Physics thanks Reiner Zorn, Thomas Voigtmann and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary Sections I and II and Figs. 1–4.

Source data

Source Data Fig. 1

The {x, y} data for Fig. 1a–c.

Source Data Fig. 3

The {x, y} data for Fig. 3.

Source Data Fig. 4

The {x, y} data for Fig. 4c.

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Guiselin, B., Scalliet, C. & Berthier, L. Microscopic origin of excess wings in relaxation spectra of supercooled liquids. Nat. Phys. 18, 468–472 (2022).

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