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Non-Gaussian statistics of the order parameter across a phase transition
Maxime Allemand1, Géraud Dupuy1, Paul Paquiez1
1Université Paris-Saclay, Institut d'Optique Graduate School, CNRS, Laboratoire Charles Fabry, Palaiseau, France.
Nature
|July 22, 2026
Summary
Researchers explored critical phenomena by measuring order parameter statistics during a phase transition in a Bose gas. They discovered non-Gaussian statistics and sign changes in high-order cumulants, revealing insights into quantum critical properties.
Area of Science:
- Quantum physics
- Condensed matter physics
Background:
- Second-order phase transitions exhibit critical scaling and universality.
- Order parameter statistics, particularly non-Gaussian distributions, are crucial for understanding critical phenomena but remain largely unexplored.
Purpose of the Study:
- To measure the full probability distribution of the order-parameter amplitude across a continuous phase transition.
- To investigate non-Gaussian statistics and their implications for critical phenomena.
Main Methods:
- Utilized single-atom-resolved detection in momentum space.
- Measured the complete probability distribution of the order-parameter amplitude.
- Reconstructed an effective potential from the probability distribution, analogous to Landau theory.
Main Results:
- Observed non-Gaussian statistics for the order parameter near the transition, characterized by non-zero high-order cumulants with abrupt sign changes.
- The effective potential showed a non-trivial minimum in the superfluid phase that vanished at the transition point.
- Numerical simulations confirmed critical scaling of cumulant sign changes and demonstrated that classical models failed to reproduce experimental behavior, unlike a low-temperature quantum model.
Conclusions:
- Order parameter statistics play a vital role in probing critical phenomena and universality.
- The study highlights the importance of non-Gaussian statistics and quantum effects in understanding phase transitions.
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