On the spectrum of the Hubbard model with infinite repulsion on anisotropic triangular ladder-type lattice

Abstract

Low-energy states of the Hubbard model with infinite electron repulsion on an anisotropic triangular strip-type lattice formed by weakly interacting linear segments are studied. The estimates of the stability region boundaries for the ferromagnetic ground state of the lattice are obtained in first order perturbation theory in the interaction between the segments. It is shown that a magnetic transition accompanied by a jumpwise variation of the total spin of the ground state from the minimum to the maximum value is possible for lattices with cyclic boundary conditions and the number of electrons greater than the number of segments by unity.

Excitation spectrum of Hubbard model with infinite electron repulsion on strip-type triangular lattices

“…For rectangular lattice strip formed by weakly interacted two‐site segments (so‐called U =∞ Hubbard ladder), the dependence of the ground‐state spin on the model parameters is described adequately on the polaron hypothesis 9, 10. Similar dependence for anisotropic triangular lattice strip is more complicated 5, 11. In order to investigate the ground‐state spin problem we will use perturbation theory in the interactions between segments and perform corresponding analytical and numerical calculations for the energy spectra of small lattice clusters.…”