Lattice polarons across the superfluid to Mott insulator transition

Abstract: We study the physics of a mobile impurity confined in a lattice, moving within a Bose-Hubbard bath at zero temperature. Within the Quantum Gutzwiller formalism, we develop a beyond-Fr\"ohlich model of the bath-impurity interaction. Results for the properties of the polaronic quasiparticle formed from the dressing of the impurity by quantum fluctuations of the bath are presented throughout the entire phase diagram, focusing on the quantum phase transition between the superfluid and Mott insulating phases. Here we find that the modification of the impurity properties is highly sensitive to the different universality classes of the transition, providing an unambiguous probe of correlations and collective modes in a quantum critical many-body environment.