M. Maksymenko, A. Honecker, R. Moessner, J. Richter, O. Derzhko
We investigate location and nature of the para-ferro transition of interacting electrons in dispersionless bands using the example of the Hubbard model on the Tasaki lattice. This case can be analyzed as a geometric site-percolation problem where different configurations appear with non-trivial weights. We provide a complete exact solution for the 1D case and develop a numerical algorithm for the 2D case. In 2D the paramagnetic phase persists beyond the uncorrelated percolation point, and the grand-canonical transition is via a first-order jump to an unsaturated ferromagnetic phase.
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http://arxiv.org/abs/1204.2110
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