| dc.description.abstract | We study the AB2 dimmer-connector 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 nite clusters, and derive some asymptotic results, valid for macroscopic
chains. We take a non-vanishing intra-dimmer 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 (2N) degenerancy of the AB2 Heisenberg chain ground
state (GS) is fully removed on going to the (more fundamental) Hubbard model, yielding a non-magnetic GS. | |
