Breathing modes of repulsive polarons in Bose-Bose mixtures

TL;DR

This paper investigates how impurities in a two-component Bose-Einstein condensate affect phase transitions and impurity dynamics, revealing that impurity interactions can induce miscible-immiscible transitions and modify breathing modes.

Contribution

It provides a detailed analysis of impurity-induced phase transitions and impurity breathing modes in Bose-Bose mixtures using numerical and variational methods.

Findings

Impurities can induce a miscible-immiscible phase transition.

Breathing modes are affected by impurity interactions and inhomogeneity.

Phonons cause damping of impurity breathing oscillations.

Abstract

We consider impurity atoms embedded in a two-component Bose-Einstein condensate in a quasi-one dimensional regime. We study the effects of repulsive coupling between the impurities and Bose species on the equilibrium of the system for both miscible and immiscible mixtures by numerically solving the underlying coupled Gross-Pitaevskii equations. Our results reveal that the presence of impurities may lead to a miscible-immiscible phase transition due to the interaction of the impurities and the two condensates. Within the realm of the Bogoliubov-de Gennes equations we calculate the quantum fluctuations due to the different types of interactions. The breathing modes and the time evolution of harmonically trapped impurities in both homogeneous and inhomogeneous binary condensates are deeply discussed in the miscible case using variational and numerical means. We show in particular that the self-trapping, the miscibility and the inhomogeneity of the trapped Bose mixture may strongly modify the low-lying excitations and the dynamical properties of impurities. The presence of phonons in the homogeneous Bose mixture gives rise to the damping of breathing oscillations of impurities width.