In half-filled quasiperiodic moiré bands, ferromagnetism occurs at interaction strengths set by real-space geometry of localized orbital overlaps, with controlled resonances far below the band gap.
Ferromagnetism vs. Antiferromagnetism in Narrow-Band Systems: Competition Between Quantum Geometry and Band Dispersion
4 Pith papers cite this work. Polarity classification is still indexing.
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abstract
Magnetism in narrow-band systems arises from the interplay between electronic correlations, quantum geometry, and band dispersion. In particular, both ferro and anti-ferro magnets are known to occur as ground states of (different) models featuring narrow bands. This poses the question of which is favored and under what conditions. In this work, we present a unified theoretical framework to investigate spin physics within narrow bands. By deriving an effective spin model, we show that the non-atomic wavefunction of the narrow bands generally favors ferromagnetic ordering, while band dispersion promotes antiferromagnetic correlations. We find that the competition between these effects gives rise to a tunable magnetic phase and rich spin phenomena. Our approach offers a systematic way to study the magnetic properties of narrow-band systems, integrating the roles of wave function, band structure, and correlation effects.
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Extended fRG calculation of the infinite-U Hubbard model on the square lattice yields a density-driven sequence of paramagnetic Fermi liquid, antiferromagnetic stripe, and Nagaoka ferromagnetic phases, with the ferromagnet displaying an incoherent flat band and two regimes separated by a Lifshitz 2D
Strong-coupling FRG for the U=∞ Hubbard model shows bandwidth and quasiparticle residue decreasing with density, polaronic continua, bad-metal behavior with magnetic correlations, and Luttinger theorem violation above low densities.
Magnetic instabilities in generic two-orbital systems are governed by the full interplay of the bare susceptibility tensor and spin interaction matrix, not solely by the quantum geometry of a single-channel susceptibility.
citing papers explorer
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Bad metal behavior and Lifshitz transition of a Nagaoka ferromagnet
Extended fRG calculation of the infinite-U Hubbard model on the square lattice yields a density-driven sequence of paramagnetic Fermi liquid, antiferromagnetic stripe, and Nagaoka ferromagnetic phases, with the ferromagnet displaying an incoherent flat band and two regimes separated by a Lifshitz 2D
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Functional renormalization group for extremely correlated electrons
Strong-coupling FRG for the U=∞ Hubbard model shows bandwidth and quasiparticle residue decreasing with density, polaronic continua, bad-metal behavior with magnetic correlations, and Luttinger theorem violation above low densities.
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Reevaluating Quantum Geometric Criteria for Itinerant Magnetic Instabilities
Magnetic instabilities in generic two-orbital systems are governed by the full interplay of the bare susceptibility tensor and spin interaction matrix, not solely by the quantum geometry of a single-channel susceptibility.