BEC immersed in a Fermi sea: Theory of static and dynamic behavior across phase separation

Abstract

We theoretically study the static and dynamic behavior of a BEC immersed in a large Fermi sea of ultracold atoms under conditions of tunable interspecies interaction. The degenerate Bose-Fermi mixture is kept in an elongated trap, typical for a single-beam optical dipole trap. We focus on the case of repulsive Bose-Fermi interaction and develop mean-field models to simulate the system over a wide range of repulsion strength. We further get analytical solutions in the regimes of phase separation and weak interaction. We obtain static density profiles and the frequency of the radial breathing mode, which is an elementary dynamic phenomenon of the mixture. Our results unveil the structure of the Bose-Fermi interface and describe the origin of the frequency shift of the breathing mode when the components become phase-separated at strong repulsion. We show that the mediated interaction between bosons induced by the Fermi sea can be understood as an adiabatic second-order mean-field effect, which is valid also beyond the weak-interaction regime for relevant experimental conditions. These results are consistent with our recent observations in a mixture of ${}^{41}$K and ${}^6$Li.

8 figures

References in corpus (12)

• Interaction-driven Dynamics of 40K / 87Rb Fermi-Bose Gas Mixtures in the Large Particle Number Limit
• Two-Element Mixture of Bose and Fermi Superfluids
• Interface Tension of Bose-Einstein Condensates
• Phase separation and collapse in Bose-Fermi mixtures with a Feshbach resonance
• Breakdown of the local density approximation in interacting systems of cold fermions in strongly anisotropic traps
• Breathing Mode of a BEC Repulsively Interacting with a Fermionic Reservoir
• Coupled Dipole Oscillations of a Mass-Imbalanced Bose and Fermi Superfluid Mixture
• Fermion-mediated interactions in a dilute Bose-Einstein condensate
• p-Wave superfluid and phase separation in atomic Bose-Fermi mixture
• Trapped Phase-Segregated Bose-Fermi Mixtures and their Collective Excitations
• Collective Excitations of Trapped Imbalanced Fermion Gases
• Finite temperature excitations of a trapped Bose-Fermi mixture

Cited by in corpus (3)

• Stability and breakdown of Fermi polarons in a strongly interacting Fermi-Bose mixture
• Interactions mediated by atoms, photons, electrons, and excitons
• Effective pair interaction between impurity particles induced by a dense Fermi gas