Research Information System
PHYSICAL REVIEW A, vol.112, no.6, 2025 (SCI-Expanded, Scopus)
An impurity immersed in a Bose condensate can form a quasiparticle known as a Bose polaron. When the impurity-boson interaction is short ranged and three-body Efimov correlations are neglected, the quasiparticle properties can be characterized in terms of the impurity-boson scattering length aIB and the condensate coherence length xi. This description remains valid irrespective of the bath density n(0). Long-ranged interactions-such as provided by Rydberg or ionic impurities-introduce an effective interaction range r(eff) as the third length scale. The interplay among these competing length scales raises the question of whether a robust description across different bath densities can still be maintained. In this study, we discuss the quasiparticle nature of long-range impurities and its dependence on the length scales n(0)(-1/3), r(eff), and xi. We employ two complementary theories-the coherent-state ansatz and the perturbative Gross-Pitaevskii theory-which incorporate beyond-Frohlich interactions. We derive an analytical expression for the beyond-Frohlich effective mass for a contact interaction and numerically compute the effective mass for long-range impurities. We argue that the coupling parameter |a(IB)|n(0)(1/3) remains the principal parameter governing the properties of the polaron. For weak (|a(IB)|n(0)(1/3)<< 1) and intermediate (|a(IB)|n(0)(1/3)similar or equal to 1) values of the coupling parameter, long-range impurities in a Bose condensate are well described as quasiparticles with a finite quasiparticle weight and a well-defined effective mass. However, the quasiparticle weight becomes significantly suppressed as the effective impurity volume is occupied by an increasing number of bath particles (r(eff)n(0)(1/3)>> 1).