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arXiv · 0912.3801

Z_2-slave-spin theory for strongly correlated fermions

A. Rüegg·S. D. Huber·M. Sigrist
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Abstract

We review a representation of Hubbard-like models that is based on auxiliary pseudospin variables. These pseudospins refer to the local charge modulo two in the original model and display a local Z_2 gauge freedom. We discuss the associated mean-field theory in a variety of different contexts which are related to the problem of the interaction-driven metal-insulator transition at half-filling including Fermi surface deformation and spectral features beyond the local approximation. Notably, on the mean-field level, the Hubbard bands are derived from the excitations of an Ising model in a transverse field and the quantum critical point of this model is identified with the Brinkman-Rice criticality of the almost localized Fermi liquid state. Non-local correlations are included using a cluster mean-field approximation and the Schwinger boson theory for the auxiliary quantum Ising model.

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A. Rüegg, S. D. Huber, M. Sigrist. 2010-04-22. Z_2-slave-spin theory for strongly correlated fermions. https://doi.org/10.1103/physrevb.81.155118

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