This paper investigates the collective oscillations of spin-polarized fermionic impurities within a Bose-Einstein condensate (BEC), exploring how these oscillations are affected by interaction strength and temperature. The study reveals that at strong interactions, the fermionic gas closely mimics the BEC's superfluid hydrodynamic modes. Increasing thermal excitations transitions the system from a collisionless to a hydrodynamic regime, mirroring behavior observed in 2D electron fluids. The researchers also observed Faraday waves in both the fermionic gas and the BEC, demonstrating synchronized flow.

Zoe Z. Yan, Yiqi Ni, Alexander Chuang, Pavel E. Dolgirev, Kushal Seetharam, Eugene Demler, Carsten Robens, Martin Zwierlein