Impurity in a heteronuclear two-component Bose mixture

Abstract

We study the fate of an impurity in an ultracold heteronuclear Bose mixture, focusing on the experimentally relevant case of a $^{41}\mathrm{K}\text{\ensuremath{-}}^{87}\mathrm{Rb}$ mixture, with the impurity in a $^{41}\mathrm{K}$ hyperfine state. Our paper provides a comprehensive description of an impurity in a BEC mixture with contact interactions across its phase diagram. We present results for the miscible and immiscible regimes, as well as for the impurity in a self-bound quantum droplet. Here, varying the interactions, we find exotic states where the impurity localizes either at the center or at the surface of the droplet.