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Functional Integrals for Correlated Fermions

H. J. Schulz
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Abstract

Functional integral methods provide a way to define mean--field theories and to systematically improve them. For the Hubbard model and similar strong--correlation problems, methods based in particular on the Hubbard--Stratonovich transformation have however been plagued by difficulties to formulate the problem in a spin--rotation invariant way. Here a formalism circumventing this problem by using a space-- and time--dependent spin reference axis is discussed. This formulation is then used to suggest a possible alternative to Nagaoka ferromagnetism in the strongly correlated Hubbard model in the vicinity of half--filling. Finally, some aspects of single--particle spectra in a simplified model for a short--range ordered antiferromagnet are discussed.

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H. J. Schulz. 1994-11-16. Functional Integrals for Correlated Fermions. https://doi.org/10.1007/bf00752352

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