Dynamics of highly unbalanced Bose-Bose mixtures: miscible vs immiscible gases

TL;DR

This paper investigates the collective excitations of a highly unbalanced Bose-Bose mixture, revealing distinct behaviors in the miscible and immiscible regimes, including analytical mode frequencies and solitonic ground states.

Contribution

It provides analytical expressions for mode frequencies in the miscible case and characterizes the solitonic ground state in the immiscible case, supported by numerical simulations.

Findings

Mode frequencies are independent of minority interaction strength in the miscible case.

Ground state can form a two-domain walls soliton in the immiscible case.

Mode behavior differs significantly across the miscible-immiscible transition.

Abstract

We study the collective modes of the minority component of a highly unbalanced Bose-Bose mixtures. In the miscible case the minority component feels an effective external potential and we derive an analytical expression for the mode frequencies. The latter is independent of the minority component interaction strength. In the immiscible case we find that the ground state can be a two-domain walls soliton. Although the mode frequencies are continuous at the transition, their behaviour is very different with respect to the miscible case. The dynamical behaviour of the solitonic structure and the frequency dependence on the inter- and intra-species interaction is numerically studied using coupled Gross-Pitaevskii equations.