Lithium Lab

Coupling a mobile hole to an antiferromagnetic spin background: transient dynamics of a magnetic polaron

Phys. Rev. X 11, 021022 (2019) arXiv:2006.06672
G. Ji, M. Xu, L. Kendrick, C. S. Chiu, J. Brüggenjürgen, D. Greif, Annabelle Bohrdt, Fabian Grusdt, Eugene Demler, M. Lebrat, M. Greiner
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.