Probing the Interface of a Phase-Separated State in a Repulsive Bose-Fermi Mixture

Area of Science:

• Quantum physics
• Ultracold atomic gases
• Bose-Fermi mixtures

Background:

• Phase separation in Bose-Fermi mixtures is crucial for understanding quantum many-body systems.
• Controlling the interface between Bose-Einstein condensates and Fermi seas is key to exploring novel quantum states.

Purpose of the Study:

• To probe the interface of a phase-separated Bose-Fermi mixture.
• To quantify the spatial overlap between Bose-Einstein condensate and Fermi sea components.
• To investigate the role of interspecies repulsion and kinetic energy on the interface properties.

Main Methods:

• Utilized a Bose-Fermi mixture of potassium-41 (Bose-Einstein condensate) and lithium-6 (Fermi sea).
• Measured three-body recombination losses to quantify residual spatial overlap.
• Varied interspecies repulsion strength.
• Compared experimental data with a numerical mean-field model.

Main Results:

• Quantified residual spatial overlap between Bose-Einstein condensate and Fermi sea.
• Demonstrated that the kinetic energy term for bosons is crucial for maintaining a thin interface.
• Observed that this effect persists far into the phase-separated regime.
• Showed that the phase transition is smoothed in finite-sized systems.

Conclusions:

• The kinetic energy of condensed bosons plays a vital role in stabilizing the interface in phase-separated Bose-Fermi mixtures.
• Finite system size leads to a smoothed phase transition, impacting the interface dynamics.
• This work provides insights into the fundamental physics of interacting quantum gases.