Bose-Hubbard polaron from weak to strong coupling

The authors perform here large-scale quantum Monte Carlo simulations in the grand-canonical ensemble to characterize a mobile impurity in a 2D Bose--Hubbard bath. They find that the polaron effective mass is a reliable probe of the Mott--superfluid transition only at weak coupling, while strong impurity--bath interactions induce MI\ifmmode\pm\else\textpm\fi{}1 bound states with suppressed mobility. The work delivers controlled benchmarks across interaction strengths and clarifies how impurity physics manifests in experimentally relevant trapped atom systems.