Ferromagnetism in correlated electron systems: Generalization of Nagaoka{close_quote}s theorem
- 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, Vol. 53, Issue 14; Other Information: PBD: Apr 1996
- Country of Publication:
- United States
- Language:
- English
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