Ferromagnetism in correlated electron systems: Generalization of Nagaoka{close_quote}s theorem

Journal Article · Mon Apr 01 04:00:00 EST 1996 · Physical Review, B: Condensed Matter

DOI:https://doi.org/10.1103/PhysRevB.53.9225· OSTI ID:280188

Kollar, M; Strack, R; Vollhardt, D ^[1]

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1. Institut fuer Theoretische Physik C, Rheinisch-Westfaelische Technische Hochschule Aachen, D-52056 Aachen (Germany)

Nagaoka{close_quote}s theorem on ferromagnetism in the Hubbard model with one electron fewer than half filling is generalized to the case where all possible nearest-neighbor Coulomb interactions (the density-density interaction {ital V}, bond-charge interaction {ital X}, exchange interaction {ital F}, and hopping of double occupancies {ital F}{sup {prime}}) are included. It is shown that for ferromagnetic exchange coupling ({ital F}{approx_gt}0) ground states with maximum spin are stable already at finite Hubbard interaction {ital U}{approx_gt}{ital U}{sub {ital c}}. For nonbipartite lattices this requires a hopping amplitude {ital t}{le}0. For vanishing {ital F} one obtains {ital U}{sub {ital c}}{r_arrow}{infinity} as in Nagaoka{close_quote}s theorem. This shows that the exchange interaction {ital F} is important for stabilizing ferromagnetism at finite {ital U}. Only in the special case {ital X}={ital t} is the ferromagnetic state stable even for {ital F}=0, provided the lattice allows the hole to move around loops. {copyright} {ital 1996 The American Physical Society.}

• OSTI ID: 280188
• Journal Information: Physical Review, B: Condensed Matter, Journal Name: Physical Review, B: Condensed Matter Journal Issue: 14 Vol. 53; ISSN 0163-1829; ISSN PRBMDO
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
BAND THEORY
COULOMB FIELD
ELECTRON GAS
EXCHANGE INTERACTIONS
FERROMAGNETISM
GROUND STATES
HAMILTONIANS
HUBBARD MODEL
STABILITY
STRONG-COUPLING MODEL