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arXiv:2511.14754 · Science Advances

Observation of critical scaling in the Bose gas universality class

Leon Kleebank, Frank Vewinger, Arturo Camacho-Guardian, Victor Romero-Rochín, Rosario Paredes, Martin Weitz, Julian Schmitt

cond-mat.quant-gasquant-phSubmitted Nov 18, 2025• Announced Nov 19, 2025• 0 citations
v1 · Nov 18, 2025v2 · Sep 17, 2026
arXivHTMLPDF

Abstract

Critical exponents characterize the divergent scaling of thermodynamic quantities near phase transitions and allow for the classification of physical systems into universality classes. While quantum gases thermalizing by interparticle interactions fall into the XY model universality class, the ideal Bose gas has been predicted to form a distinct universality class whose signatures have not yet been revealed experimentally. Here, we report the observation of critical scaling in a two-dimensional quantum gas of essentially noninteracting photons, which thermalize by radiative contact to a reservoir of molecules inside a microcavity. By measuring the spatial correlations near the condensation transition, we determine the critical exponent for the correlation length to be $ν= 0.52(3)$. Our results constitute a first experimental test of the long-standing scaling predictions for the Bose gas universality class.

Journal reference
Sci. Adv. 12, eaee2942 (2026)
DOI
10.1126/sciadv.aee2942
Comments
10 pages, 6 figures

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