Abstract
Understanding the interplay between charge and spin and its effects on transport is a ubiquitous challenge in quantum many-body systems. In the Fermi-Hubbard model, this interplay is thought to give rise to magnetic polarons, whose dynamics may explain emergent properties of quantum materials such as high-temperature superconductivity. In this work, we use a cold-atom quantum simulator to directly observe the formation dynamics and subsequent spreading of individual magnetic polarons. Measuring the density- and spin-resolved evolution of a single hole in a 2D Hubbard insulator with short-range antiferromagnetic correlations reveals fast initial delocalization and a dressing of the spin background, indicating polaron formation. At long times, we find that dynamics are slowed down by the spin exchange time, and they are compatible with a polaronic model with strong density and spin coupling. Our work enables the study of out-of-equilibrium emergent phenomena in the Fermi-Hubbard model, one dopant at a time.
Highlights
Interactions between charge carriers and magnetic excitations can drastically alter the transport properties of a many-body system
We find that dynamics are slowed down by the spin exchange time, and they are compatible with a polaronic model with strong density and spin coupling
Our work enables the study of out-of-equilibrium emergent phenomena in the Fermi-Hubbard model, one dopant at a time
Summary
Interactions between charge carriers and magnetic excitations can drastically alter the transport properties of a many-body system. In the two-dimensional Hubbard model, the competition between charge delocalization, related to the nearest-neighbor tunneling energy t, and antiferromagnetism, set by the spin exchange energy J, already results in intricate dynamics at the level of a single charge excitation This iconic problem has attracted extensive theoretical attention [1,2,3,4,5,6,7,8,9] and can be reinterpreted as the creation and dispersion of a magnetic polaron, a charge carrier dressed by the magnetic background with renormalized properties. We quantitatively validate our understanding of the spin dynamics by comparing them to a phenomenological model of the formation and departure of a spin polaron
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