Microscopic evolution of doped Mott insulators from polaronic to Fermi liquid regime

The competition between antiferromagnetism and hole motion in two-dimensional Mott insulators lies at the heart of a doping-dependent transition from an anomalous metal to a conventional Fermi liquid. Condensed matter experiments suggest that charge carriers change their nature within this crossover, but a full understanding remains elusive. We study this regime by preparing a cold fermionic gas in an optical lattice at a temperature around the superexchange energy. It is imaged using a quantum gas microscope with full spin and density resolution allowing the extraction of a wide range of correlators. Crucial to deeper understanding is the capability to calculate higher order correlators as well as common observables from solid states systems such as the spin susceptibility, all of which are studied as a function of doping level. While at low doping the system exhibits magnetic polarons, i.e. holes with a dressed cloud of spins, higher doping leads to the metallic Fermi liquid regime characterised by incommensurate magnetic fluctuations and altered correlations. The crossover is completed for hole dopings around 30%. Several theoretical models are benchmarked and their agreement with the experiment in different doping regimes discussed.
J.Koepsell et al., arXiv:2009.04440 (2020)