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Ferromagnetism in the Hubbard model on the square lattice: Improved instability criterion for the Nagaoka state
Author(s) -
Wurth P.,
Uhrig G.,
MüllerHartmann E.
Publication year - 1996
Publication title -
annalen der physik
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.009
H-Index - 68
eISSN - 1521-3889
pISSN - 0003-3804
DOI - 10.1002/andp.2065080204
Subject(s) - square lattice , spins , condensed matter physics , physics , hubbard model , instability , ferromagnetism , lattice (music) , hamiltonian (control theory) , quantum mechanics , ising model , superconductivity , mathematics , mathematical optimization , acoustics
The instability of the fully polarized ferromagnetic state (Nagaoka state) with respect to single spin flips is re‐examined for the Hubbard model on the square lattice with a large family of variational wave functions which include correlation effects of the majority spins in the vicinity of the flipped spin. We find a critical hole density of δ cr = 0.251 for U = ∞ and a critical coupling of U cr = 77.7 t . Both values improve previous variational results considerably.