# The Hubbard model beyond the two-pole approximation: a composite operator method study

@article{Avella2014TheHM, title={The Hubbard model beyond the two-pole approximation: a composite operator method study}, author={Adolfo Avella}, journal={The European Physical Journal B}, year={2014}, volume={87}, pages={1-18} }

Within the framework of the Composite Operator Method, a three-pole solution for the two-dimensional Hubbard model is presented and analyzed in detail. In addition to the two Hubbard operators, the operatorial basis comprises a third operator describing electronic transitions dressed by nearest-neighbor spin fluctuations. These latter, compared to charge and pair fluctuations, are assumed to be preeminent in the region of model-parameter space — small doping, low temperature and large on-site…

## 9 Citations

Fermi surface evolution of the 2D Hubbard model within a novel four-pole approximation

- PhysicsAIP Advances
- 2018

We present a novel solution of the 2D Hubbard model in the framework of the Composite Operator Method within a four-pole approximation. We adopt a basis of four fields: the two Hubbard operators plus…

COM(3p) Solution of the 2D Hubbard Model: Momentum-Resolved Quantities

- Physics
- 2014

Recently, within the framework of the composite operator method, it has been proposed that a three-pole solution for the two-dimensional Hubbard model (Eur. Phys. J. B 87, 45 (2014)),which is still…

Local properties of the t-J model in a two-pole approximation within COM

- PhysicsJournal of Magnetism and Magnetic Materials
- 2021

Single-particle properties of the Hubbard model in a novel three-pole approximation

- Physics
- 2017

Abstract We study the 2D Hubbard model using the Composite Operator Method within a novel three-pole approximation. Motivated by the long-standing experimental puzzle of the single-particle…

A generalized mean-field theory for the t-J model: the single-pole COM solution

- PhysicsThe European Physical Journal Special Topics
- 2019

We have reported the most general mean-field approximation for the t-J model obtained in the framework of the Composite Operator Method within the simplest one-pole approximation. The…

Strongly Correlated Electron Systems: an operatorial perspective

- Physics
- 2017

Abstract We discuss the operatorial approach to the study of strongly correlated electron systems and show how the exact solution of target models on small clusters chosen ad-hoc (minimal models) can…

Composite Operator Method Analysis of the Underdoped Cuprates Puzzle

- Physics
- 2014

The microscopical analysis of the unconventional and puzzling physics of the underdoped cuprates, as carried out lately by means of the composite operator method (COM) applied to the 2D Hubbard…

Modified equation of motion approach for metallic ferromagnetic systems with the correlated hopping interaction

- Physics
- 2016

We consider the extended Hubbard model with included nearest neighbors off-diagonal correlated hopping interaction. This model is analyzed using the modified equation of motion (EOM) approach with…

London penetration depth in the ensemble of spin polarons of cuprate superconductors

- PhysicsThe European Physical Journal B
- 2018

Abstract
Within the spin-polaron concept for hole-doped cuprates superconductors the temperature and doping dependence of the London penetration depth λ is studied. To calculate λ we developed a…

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