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Hund-projected Kanamori model: An effective description of Hund's metals near the Mott insulating regime

Johan Carlström

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Phys. Rev. B 113, 165135 – Published 17 April, 2026

DOI: https://doi.org/10.1103/v7zb-8ndn

Abstract

Hund's coupling plays a decisive role in shaping electron correlations of multi-orbital systems, giving rise to a class of materials—Hund's metals—that combine local-moment physics with metallic transport. Here, we derive an effective low-energy description of such a system near the Mott insulating regime, starting from the multi-orbital Hubbard-Kanamori Hamiltonian and projecting onto the high-spin manifold favored by Hund's first rule. The resulting Hund-projected Kanamori model captures the interplay between carrier motion and magnetic correlations in the presence of strong Hund's coupling. In the undoped limit, the model reduces to a spin-N/2 Heisenberg system with suppressed quantum fluctuations, approaching the classical limit for realistic five-band configurations. Upon doping, carrier motion couples strongly to the spin background and drives ferromagnetic correlations through a Hund-enhanced kinetic mechanism analogous to, but much stronger than, Nagaoka ferromagnetism. Owing to its reduced sign problem, the model can be addressed with advanced path-integral methods to determine quasiparticle structure and effective interactions between carriers—quantities that are challenging to obtain with other methods. This framework establishes a microscopic bridge between the Kanamori model and the emergent magnetic and transport phenomena characteristic of Hund's metals.

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Phys. Rev. B 113, 165135– Published 17 April, 2026
  • Received 1 December 2025
  • Revised 2 February 2026
  • Accepted 2 March 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by Bibsam.

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