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arXiv · 0712.3431

The breakdown of the mean-field description of the Nagaoka phase

Evgueny Kochetov·Fabio L. Braghin·Alvaro Ferraz
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Abstract

We discuss the relevance of the improved mean-field slave-fermion theory to describe the Nagaoka ($U=\infty$) limit of the Hubbard model. In this theory the crucial on-site constraint of no double electron occupancy is taken into account rigorously prior to the mean-field approximation. At one-loop approximation the effective mean-field action shows a long-range ferromagnetic order over the whole doping range. This indicates that the slave-fermion mean-field theory does not constitute an appropriate framework to describe the physics of the Nagaoka phase. We discuss the drawbacks of this mean-field theory and present some results on the derivation of a low-energy effective spin action to describe the Nagaoka phase beyond the mean-field approximation.

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Evgueny Kochetov, Fabio L. Braghin, Alvaro Ferraz. 2008-09-04. The breakdown of the mean-field description of the Nagaoka phase. https://doi.org/10.1103/physrevb.78.115109

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