Polaronic mechanism of Nagaoka ferromagnetism in Hubbard models

Abstract

The search for elusive Nagaoka-type ferromagnetism in the Hubbard model has recently enjoyed renewed attention with the advent of a variety of experimental platforms enabling its realization, including moiré materials, quantum dots, and ultracold atoms in optical lattices. Here, we demonstrate a universal mechanism for Nagaoka ferromagnetism (that applies to both bipartite and nonbipartite lattices) based on the formation of ferromagnetic polarons consisting of a dopant dressed with polarized spins. Using large-scale density-matrix renormalization group calculations, we present a comprehensive study of the ferromagnetic polaron in an electron-doped Hubbard model, establishing various polaronic properties such as its size and energetics. Moreover, we systematically probe the internal structure of the magnetic state$\unicode{x2014}$through the use of pinning fields and three-point spin-charge-spin correlation functions$\unicode{x2014}$for both the single-polaron limit and the high-density regime of interacting polarons. Our results highlight the crucial role of mobile polarons in the birth of global ferromagnetic order from local ferromagnetism and provide a unified framework to understand the development and demise of the Nagaoka-type ferromagnetic state across dopings.

14 pages, 13 figures

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Cited by in corpus (10)

• Nagaoka ferromagnetism in doped Hubbard models in optical lattices
• Finite-Temperature Kinetic Ferromagnetism in the Square Lattice Hubbard Model
• Itinerant ferromagnetism in an SU(3) Fermi-Hubbard model at finite temperatures: A dynamical mean-field theory study
• Functional renormalization group for extremely correlated electrons
• Shaping Magnetic Order by Local Frustration for Itinerant Fermions on a Graph
• Optimal array geometries for kinetic magnetism and Nagaoka polarons
• Bad Metal Behavior and Lifshitz Transition of a Nagaoka Ferromagnet
• Geometric Frustration Assisted Kinetic Ferromagnetism in Doped Mott Insulators
• Itinerant magnetism in Hubbard models with long-range interactions
• Generalized Nagaoka ferromagnetism accompanied by flavor-selective Mott states in an SU($N$) Fermi-Hubbard model