Many-body bound states and induced interactions of charged impurities in a bosonic bath

TL;DR

This paper explores how charged impurities interact within a bosonic medium, revealing different regimes of bipolaron formation and emphasizing the importance of numerical methods for understanding complex quantum impurity systems.

Contribution

It provides a detailed quantum Monte Carlo analysis of impurity-bath interactions, identifying three distinct bipolaron regimes and highlighting bath-induced interactions.

Findings

Identification of three bipolaron regimes based on atom-ion potential strength

Discovery of many-body bound states only when two-body bound states exist

Strong bath-induced interactions between ionic polarons

Abstract

Induced interactions and bound states of charge carriers immersed in a quantum medium are crucial for the investigation of quantum transport. Ultracold atom-ion systems can provide a convenient platform for studying this problem. Here, we investigate the static properties of one and two ionic impurities in a bosonic bath using quantum Monte Carlo methods. We identify three bipolaronic regimes depending on the strength of the atom-ion potential and the number of its two-body bound states: a perturbative regime resembling the situation of a pair of neutral impurities, a non-perturbative regime that loses the quasi-particle character of the former, and a many-body bound state regime that can arise only in the presence of a bound state in the two-body potential. We further reveal strong bath-induced interactions between the two ionic polarons. Our findings show that numerical simulations are indispensable for describing highly correlated impurity models.