Fermi Polaron in atom—ion hybrid systems

Charged quasiparticles dressed by the low excitations of an electron gas, constitute one of the fundamental pillars for understanding quantum many-body effects in some materials. Quantum simulation of quasiparticles arising from atom-ion hybrid systems may shed light on solid-state uncharted regimes. Here we investigate the ionic Fermi polaron consisting of a charged impurity interacting with a polarized Fermi bath. Employing state-of-the-art quantum Monte Carlo techniques tailored for strongly correlated systems, we characterize the charged quasiparticle by computing the energy spectrum, quasiparticle residue, and effective mass, as well as the structural properties of the system. Our findings in the weak coupling regime agree with field-theory predictions within the ladder approximation. However, stark deviations emerge in the strongly interacting regime attributed to the vastly large density inhomogeneity around the ion, resulting in strong correlations for distances on the order of the atom-ion potential range. Moreover, we find a smooth polaron-molecule transition for strong coupling, in contrast with the neutral case, where the transition smoothens only for finite temperature and finite impurity density. This study may provide valuable insights into alternative solid-state systems such as Fermi excitons polarons in atomically thin semiconductors beyond the short-range limit.