1995/12/08 by P. Wurth, G. Uhrig, E. Mueller-Hartmann
Physics and Astronomy · #cond-mat
published as Annalen der Physik 5, 148 (1996) · 10 pages + 1 figure, submitted as uuencoded compressed ps-file, to be published in Annalen der Physik
arxiv created 1995/12/08 · arxiv updated 2009/11/30
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 δcr = 0.251 for U = ∞ and a critical coupling of Ucr = 77.7 t. Both values improve previous variational results considerably.