Beyond-Mean-Field Effects in Rabi-Coupled Two-Component Bose-Einstein Condensate

Year: 2021

Authors: Lavoine L.; Hammond A.; Recati A.; Petrov D.S.; Bourdel T.

Autors Affiliation: Laboratoire Charles Fabry, UMR 8501, Institut d?Optique, CNRS, University Paris-Saclay, Avenue Augustin Fresnel, 91127 Palaiseau CEDEX, France; INO-CNR BEC Center and Dipartimento di Fisica, Universita degli Studi di Trento, 38123 Povo, Italy and Trento Institute for Fundamental Physics and Applications, INFN, 38123 Trento, Italy; University Paris-Saclay, CNRS, LPTMS, 91405 Orsay, France

Abstract: We theoretically calculate and experimentally measure the beyond-mean-field (BMF) equation of state in a coherently coupled two-component Bose-Einstein condensate (BEC) in the regime where averaging of the interspecies and intraspecies coupling constants over the hyperfine composition of the single-particle dressed state predicts the exact cancellation of the two-body interaction. We show that with increasing the Rabi-coupling frequency ?, the BMF energy density crosses over from the nonanalytic Lee-Huang-Yang scaling ?n5/2 to an expansion in integer powers of density, where, in addition to a two-body BMF term ?n2?, there emerges a repulsive three-body contribution ?n3/?. We experimentally evidence these two contributions, thanks to their different scaling with ?, in the expansion of a Rabi-coupled two-component K39 condensate in a waveguide. By studying the expansion with and without Rabi coupling, we reveal an important feature relevant for observing BMF effects and associated phenomena in mixtures with spin-asymmetric losses: Rabi coupling helps preserve the spin composition and thus prevents the system from drifting away from the point of the vanishing mean field.


Volume: 127 (20)      Pages from: 203402-1  to: 203402-6

DOI: 10.1103/PhysRevLett.127.203402