Title: Ferrimagnetism in the Hubbard, dimmer-connector 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 AB₂ "dimmer-connector" chain within a generalized Hubbard model, which contains site-dependent 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 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 (2^N) 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.

Key words: Hubbard model, Heisenberg model, ferrimagnetic order, frustration, lozenge lattice, dimmer
PACS: 73.90.+f, 75.10.Lp, 75.10-75.25

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