Microscopic control and dynamics of a Fermi-Hubbard system

Abstract

Strongly correlated systems have rich and intriguing behaviors that have been at the focal point of modern condensed-matter physics. One promising research direction is the study of the Fermi-Hubbard model, which is thought to describe the essential physics of the cuprates and is naturally realized with ultracold atoms in optical lattices. The development of single-site control and readout on this platform has allowed for new methods in creating and studying states in the Fermi-Hubbard model. In this thesis, we discuss the engineering of low-entropy correlated states using a novel technique. By preparing a gapped band-insulator in the presence of an entropy reservoir, we create states with an entropy per particle of 0.016(3) k_B. We then demonstrate that the low-entropy band insulator can be used as a resource for creating strongly correlated states; by dynamically manipulating the on-site potentials we are able to convert the uncorrelated band insulator into a correlated Mott insulator. We also investigate if heating is responsible for the increase in entropy when creating the correlated phase and determine that it does not play a dominant role. In a separate experiment, we leverage the single-site manipulation capabilities in a different way by creating a single localized hole dopant in an antiferromagnetic state. We then allow the hole to delocalize by suddenly removing its pinning potential and study the resulting density and spin correlation evolution. As the hole delocalizes, we find that it displaces the surrounding spin correlations in a trajectory that is initially controlled by quantum interference. At later times, the hole delocalizes at a rate that scales with the spin exchange energy, revealing that the presence of magnetism fundamentally alters charge transport. These developments demonstrate continued progress in optical lattice quantum simulators and how they can play a role in unraveling the mysteries of the Fermi-Hubbard model.