Condensed Matter Physics, 2010, vol. 13, No. 1, p. 13704:18
DOI:10.5488/CMP.13.13704
Title:
Ferrimagnetism in the Hubbard, dimmerconnector frustrated chain
Author(s):

J. Rössler
(Departamento de Física, Facultad de Ciencias, Universidad de Chile, Casilla 653, Santiago, Chile)
,


D. Mainemer
(Departamento de Física, Facultad de Ciencias, Universidad de Chile, Casilla 653, Santiago, Chile)

We study the AB_{2} "dimmerconnector"
chain within a generalized Hubbard model, which contains
sitedependent parameters, and different chemical potentials for
A and B sites. Considering one electron per atom, we
carry out exact calculations for finite clusters, and derive some
asymptotic results, valid for macroscopic chains. We take a
nonvanishing intradimmer electron hopping, thus departing from the
condition of a bipartite lattice. In spite of that, the system
persists ferrimagnetic in some region of the parameter space, thus
generalizing a theorem of Lieb for bipartite lattices. A somewhat
surprising result is that the ferrimagnetic phase is possible, even
for a very large chemical potential jump between A and B
sites. In another respect, we show that a previously reported
macroscopic (2^{N}) degenerancy of the AB_{2}
Heisenberg chain ground state (GS) is fully removed on going to the
(more fundamental) Hubbard model, yielding a nonmagnetic GS.
Key words:
Hubbard model, Heisenberg model, ferrimagnetic order, frustration, lozenge lattice, dimmer
PACS: 73.90.+f, 75.10.Lp, 75.1075.25
