Observation of Nagaoka polarons in a Fermi-Hubbard quantum simulator

• 成果类型: Article
• 署名作者: Lebrat, Martin; Xu, Muqing; Kendrick, Lev Haldar; Kale, Anant; Gang, Youqi; Seetharaman, Pranav; Morera, Ivan; Khatami, Ehsan; Demler, Eugene; Greiner, Markus
• 署名单位: Harvard University; California State University System; San Jose State University; University of Barcelona; University of Barcelona; Swiss Federal Institutes of Technology Domain; ETH Zurich
• 刊物名称: Nature
• ISSN/ISSBN: 0028-6961
• DOI: 10.1038/s41586-024-07272-9
• 发表日期: 2024-05-09
• 关键词: ferromagnetic state; instability; MODEL; excitations; physics; STABILITY; magnetism

摘要

Quantum interference can deeply alter the nature of many-body phases of matter1. In the case of the Hubbard model, Nagaoka proved that introducing a single itinerant charge can transform a paramagnetic insulator into a ferromagnet through path interference2-4. However, a microscopic observation of this kinetic magnetism induced by individually imaged dopants has been so far elusive. Here we demonstrate the emergence of Nagaoka polarons in a Hubbard system realized with strongly interacting fermions in a triangular optical lattice5,6. Using quantum gas microscopy, we image these polarons as extended ferromagnetic bubbles around particle dopants arising from the local interplay of coherent dopant motion and spin exchange. By contrast, kinetic frustration due to the triangular geometry promotes antiferromagnetic polarons around hole dopants7. Our work augurs the exploration of exotic quantum phases driven by charge motion in strongly correlated systems and over sizes that are challenging for numerical simulation8-10. Emergence of Nagaoka polarons and kinetic magnetism is observed in a Hubbard system realized with strongly interacting fermions trapped in a triangular optical lattice.