Persistent breather and dynamical symmetry in a unitary Fermi gas

Year: 2025

Authors: Sun DL., Min J., Yan XC., Wang L., Xie X., Wu XZ., Maki J., Zhang SZ., Peng SG., Zhan MS., Jiang KJ.

Autors Affiliation: Chinese Acad Sci, Innovat Acad Precis Measurement Sci & Technol, State Key Lab Magnet Resonance & Atom & Mol Phys, Wuhan 430071, Peoples R China; Univ Chinese Acad Sci, Beijing 100049, Peoples R China; Univ Trento, Pitaevskii BEC Ctr, CNR INO, I-38123 Trento, Italy; Univ Trento, Dipartimento Fis, I-38123 Trento, Italy; Univ Hong Kong, Dept Phys, Hong Kong, Peoples R China; Univ Hong Kong, Hong Kong Inst Quantum Sci & Technol, Hong Kong, Peoples R China; Wuhan Inst Quantum Technol, Wuhan 430206, Peoples R China.

Abstract: SO(2,1) dynamical symmetry makes a remarkable prediction that the breathing oscillation of a scale-invariant quantum gas in an isotropic harmonic trap is isentropic and can persist indefinitely. In two dimensions, this symmetry is broken due to quantum anomaly in the strongly interacting range, and consequently the lifetime of the breathing mode becomes finite. The persistent breather in a strongly interacting system has so far not been realized. Here, we experimentally achieve the long-lived breathing mode in a three-dimensional unitary Fermi gas, which is protected by the SO(2,1) symmetry. The nearly perfect SO(2,1) symmetry is realized by loading the ultracold Fermi gas in an isotropic trap and tuning the interatomic interaction to resonance. The breathing mode oscillates at twice the trapping frequency even for large excitation amplitudes. The ratio of damping rate to oscillation frequency is as small as 0.002, providing an interacting persistent breather. The oscillation frequency and damping rate are nearly constant for different atomic densities and temperatures, demonstrating the robustness of the SO(2,1) symmetry in three dimensions. The factors that lead to the residual damping have also been clarified. This work opens the way to study many-body nonequilibrium dynamics related to the dynamical symmetry.

Journal/Review: PHYSICAL REVIEW A

Volume: 111 (5)      Pages from: 53317-1  to: 53317-11

More Information: This work is supported by the National Key R&D Program under Grant No. 2022YFA1404102; the National Natural Science Foundation of China under Grants No. U23A2073, No. 12374250, and No. 12121004; Chinese Academy of Sciences under Grant No. YJKYYQ20170025; the Natural Science Foundation of Hubei Province under Grant No. 2021CFA027; the Natural Science Foundation of Wuhan under Grant No. 2024040701010063; and Innovation Program for Quantum Science and Technology under Grant No. 2023ZD0300401. S.Z. is supported by HK GRF Grants No. 17304820 and No. 17313122, CRF Grant No. C7012-21G, and a RGC Fellow-ship Award No. HKU RFS2223-7S03.
KeyWords: Collective Excitations; Universal Dynamics
DOI: 10.1103/PhysRevA.111.053317