Dipole dynamics of an interacting bosonic mixture

TL;DR

This study investigates the coupled dipole oscillations in a two-species Bose-Einstein condensate with tunable interactions, revealing how strong interspecies attraction influences collective modes.

Contribution

It provides the first detailed experimental and numerical analysis of dipole dynamics across a range of interspecies interactions in an asymmetric bosonic mixture.

Findings

Dipole frequencies vary with interspecies interaction strength.

Strong attraction leads to mode behavior dominated by trap and population imbalance.

Experimental results align with coupled Gross-Pitaevskii equation simulations.

Abstract

We unravel the coupled dipole dynamics of a two-species Bose-Einstein condensate with tunable interspecies interaction. We produce a degenerate mixture of $^{41}$K-$^{87}$Rb in an optical trap and we study the dipole oscillations of both atomic species in the linear response regime. Varying the interspecies interaction from the weakly to the strongly attractive side, we measure the frequencies and the composition of the two dipole eigenmodes. For enough strong interactions, even beyond the mean-field collapse, we find that the frequency of the low-energy eigenmode is determined only by the bare trap frequencies and the species population imbalance. The experimental results are well reproduced by numerical simulations based on two coupled Gross-Pitaevskii equations. Our findings provide a detailed picture of the dipole excitations in asymmetric bosonic mixtures.