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

TL;DR

This study uses a cold-atom quantum simulator to observe the formation and dynamics of magnetic polarons in a 2D Hubbard insulator, revealing insights into charge-spin interactions relevant to quantum materials.

Contribution

First direct observation of magnetic polaron formation and spreading dynamics in a 2D Hubbard model using cold-atom quantum simulation.

Findings

Rapid initial delocalization of a single hole

Polaron formation indicated by spin background dressing

Long-time dynamics slowed by spin exchange interactions

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.