Odd-parity effect and scale-dependent viscosity in atomic quantum gases

Year: 2025

Authors: Maki J., Gran U., Hofmann J.

Autors Affiliation: Univ Konstanz, Dept Phys, Constance, Germany; Univ Trento, Pitaevskii BEC Ctr, CNR INO, Trento, Italy; Univ Trento, Dipartimento Fis, Trento, Italy; Chalmers Univ Technol, Dept Phys, Gothenburg, Sweden; Gothenburg Univ, Dept Phys, Gothenburg, Sweden; Stockholm Univ, Nordita, Stockholm, Sweden; KTH Royal Inst Technol, Stockholm, Sweden.

Abstract: Two-dimensional electron gases are predicted to possess an anomalous tomographic transport regime that is marked by an odd-even effect in the relaxation times, with odd-parity deformations of the Fermi surface becoming long-lived in comparison to even-parity ones. In this work, we establish that neutral two-component atomic Fermi gases also exhibit this tomographic effect. By diagonalizing the Fermi liquid collision integral, we identify odd-parity modes with anomalously long lifetimes below temperatures T <= 0.15TF, which is within reach of cold atom experiments. Furthermore, in contrast to electron gases, we find that the odd-even effect in neutral gases is widely tuneable with interactions along the BCS-BEC crossover and is suppressed on the BEC side. We propose as an experimental signature of the odd-even effect the damping rate of quadrupole oscillations, which is anomalously enhanced due to the presence of long-lived odd-parity modes. Our findings suggest that the dynamics of two-dimensional Fermi gases is richer than previously thought and should include additional long-lived modes. Journal/Review: COMMUNICATIONS PHYSICS

Volume: 8 (1)      Pages from: 319-1  to: 319-7

More Information: J.M. is partially supported by the Provincia Autonoma di Trento. This work is supported by Vetenskapsradet (Grant Nos. 2020-04239 and 2024-04485), the Olle Engkvist Foundation (Grant No. 233-0339), the Knut and Alice Wallenberg Foundation (Grant No. KAW 2024.0129), and Nordita. The computations were enabled by resources provided by the National Academic Infrastructure for Supercomputing in Sweden (NAISS) at Linkoping University, partially funded by the Swedish Research Council through grant agreement no. 2022-06725.
KeyWords: Transverse Zero Sound; Electron Theory; Fermi; Thermodynamics; Metals
DOI: 10.1038/s42005-025-02231-w