Electron correlations in the two-dimensional Hubbard model: A group-theoretical and numerical study

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Abstract
The Lanczos algorithm has been applied to the Hubbard model on a 4×4 square lattice and several equal-time correlation functions have been evaluated. This computation has been made possible by a classification of all the irreducible representations of the space symmetry group, which allowed a considerable reduction of the dimension of the Hilbert space of the system. Such an analysis is quite general and might be useful in other physical applications. Our results shed light on the effects of doping on the magnetic ordering, suggest a spin-charge decoupling at large U, and show a remarkable reduction of the quasiparticle weight at strong coupling.