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Cumulant theory of the unitary Bose gas: Prethermal and Efimovian dynamics

TitleCumulant theory of the unitary Bose gas: Prethermal and Efimovian dynamics
Publication TypeJournal Article
Year of Publication2020
AuthorsV.. E. Colussi, H.. Kurkjian, M.. Van Regemortel, S.. Musolino, J.. van de Kraats, M.. Wouters, and S.. J. J. M. F. Kokkelmans
JournalPhys. Rev. A
Date Publisheddec

We study the quench of a degenerate ultracold Bose gas to the unitary regime, where interactions are as strong as allowed by quantum mechanics. We lay the foundation of a cumulant theory able to simultaneously capture the three-body Efimov effect and ergodic evolution. After an initial period of rapid quantum depletion, a universal prethermal stage is established, characterized by a kinetic temperature and an emergent Bogoliubov dispersion law, while the microscopic degrees of freedom remain far from equilibrium. Integrability is then broken by higher-order interaction terms in the many-body Hamiltonian, leading to a momentum-dependent departure from power law to decaying exponential behavior of the occupation numbers at large momentum. We also find signatures of the Efimov effect in the many-body dynamics and make a precise identification between the observed beating phenomenon and the binding energy of an Efimov trimer. Throughout the paper, our predictions for a uniform gas are quantitatively compared with experimental results for quenched unitary Bose gases in uniform potentials.