High-order correlation effects in the two-dimensional Hubbard model

Abstract

The electronic states of the two-dimensional Hubbard model are investigated by means of a 4-pole approximation within the Composite Operator Method. In addition to the conventional Hubbard operators, we consider other two operators which come from the hierarchy of the equations of motion and carry information regarding nearest-neighbor spin and charge configurations. By means of this operatorial basis, we can study the physics related to the energy scale of J=4t^2/U in addition to the one of U. Present results show relevant physical features, well beyond those previously obtained by means of a 2-pole approximation, such as a four-band structure with shadow bands and a quasi-particle peak at the Fermi level. The Fermi level stays pinned to the band flatness located at (pi,0)-point within a wide range of hole-doping (0 <= delta <= 0.15). A comprehensive analysis of double occupancy, internal energy, specific heat and entropy features have been also performed. All reported results are in excellent agreement with the data of numerical simulations.

13 pages, 8 figures

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• Composite Operator Method analysis of the underdoped cuprates puzzle
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• Charge dynamics of correlated electrons: Variational description with inclusion of composite fermions
• Exact solution of the 1D Hubbard model in the atomic limit with inter-site magnetic coupling
• Analysis of the Disorder-Induced Zero Bias Anomaly in the Anderson-Hubbard Model
• Spontaneous layer selective Mott phase in the bilayer Hubbard model
• The composite operator method route to the 2D Hubbard model and the cuprates
• Pseudogap and the specific heat of high $T_c$ superconductors
• Topological charge excitations and Green's function zeros in paramagnetic Mott insulators
• Local properties of the t-J model in a two-pole approximation within COM
• COM(3p) solution of the 2D Hubbard model: momentum resolved quantities