arXiv subjects

Frédéric Mila

Publications and source records attributed to Frédéric Mila.

110 records · Page 7Linked to original sources

arXiv1996

Ferromagnetism in multi--band Hubbard models: From weak to strong Coulomb repulsion

We propose a new mechanism which can lead to ferromagnetism in Hubbard models containing triangles with different on-site energies. It is based on an effective Hamiltonian that we derive in the strong coupling limit. Considering a one-dimensional realization of the model, we show that in the quarter-filled, insulating case the ground-state is actually ferromagnetic in a very large parameter range going from Tasaki's flat-band limit to the strong coupling limit of the effective Hamiltonian. This result has been obtained using a variety of analytical and numerical techniques. Finally, the same results are shown to apply away from quarter-filling, in the metallic case.

cond-mat↗

arXiv1995

Spectral function of the 1D Hubbard model in the $U\to +\infty $ limit

We show that the one-particle spectral functions of the one-dimensional Hubbard model diverge at the Fermi energy like $|ω-\varepsilon_F|^{-3/8}$ in the $U\to +\infty $ limit. The Luttinger liquid behaviour $|ω-\varepsilon_F|^α$, where $α\to 1/8$ as $U\to +\infty $, should be limited to $|ω-\varepsilon_F| \sim t^2/U$ (for $U$ large but finite), which shrinks to a single point, $ω=\varepsilon_F$,in that limit. The consequences for the observation of the Luttinger liquid behaviour in photoemission and inverse photoemission experiments are discussed.

cond-mat↗