Ionic polaron in a Bose-Einstein condensate

TL;DR

This paper investigates the complex behavior of a charged impurity in a Bose-Einstein condensate, revealing a transition from weakly interacting polaronic states to many-body bound states with unique correlations, relevant for ultracold atom-ion experiments.

Contribution

It introduces a detailed analysis of ionic polarons in a BEC, highlighting a transition between perturbative and strongly bound many-body states using quantum Monte Carlo simulations.

Findings

Identification of a transition between weak and strong atom-ion interactions.

Discovery of a many-body bound state with vanishing quasi-particle residue.

Analysis of nontrivial atom-ion and atom-atom correlation functions.

Abstract

The presence of strong interactions in a many-body quantum system can lead to a variety of exotic effects. Here we show that even in a comparatively simple setup consisting of a charged impurity in a weakly interacting bosonic medium the competition of length scales gives rise to a highly correlated mesoscopic state. Using quantum Monte Carlo simulations, we unravel its vastly different polaronic properties compared to neutral quantum impurities. Moreover, we identify a transition between the regime amenable to conventional perturbative treatment in the limit of weak atom-ion interactions and a many-body bound state with vanishing quasi-particle residue composed of hundreds of atoms. In order to analyze the structure of the corresponding states we examine the atom-ion and atom-atom correlation functions which both show nontrivial properties. Our findings are directly relevant to experiments using hybrid atom-ion setups that have recently attained the ultracold regime.