Eur. Phys. J. B 20, 303-311 (2001)
https://doi.org/10.1007/PL00011101

The two-dimensional t-t'-U model as a minimal model for cuprate materials

¹ Dipartimento di Fisica "E.R. Caianiello"- Unità INFM di Salerno, Università degli Studi di Salerno, 84081 Baronissi (SA), Italy
² Department of Applied Physics, Seikei University, Tokyo 180, Japan

Corresponding author: ^a avella@sa.infn.it

Received: 29 March 2000
Revised: 10 August 2000
Published online: 15 April 2001

Abstract

The addition to the Hubbard Hamiltonian of a t' diagonal hopping term, which is considered to be material dependent for high-T_c cuprate superconductors, is generally suggested to obtain a model capable to describe the physics of high-T_c cuprate materials. In this line of thinking, the two-dimensional t-t'-U model has been studied by means of the Composite Operator Method, which allows to determine the dynamics in a fully self-consistent way by use of symmetry requirements, as the ones coming from the Pauli principle. At first, some local quantities have been calculated to be compared with quantum Monte Carlo data. Then, the structure of the energy bands, the shape of the Fermi surface and the position of the van Hove singularity have been computed as functions of the model parameters and studied by the light of the available experimental data. The results of our study show that there exists two sets of parameters that allows the model to describe the relevant features of the 1-layer compounds NdCe_xCuO₄ and LaSr_xCuO₄. On the other hand, for the 2-layer compound YBa₂Cu₃O is not possible to find a reasonable set of parameters which could reproduce the position of the van Hove singularity as predicted by ARPES experiments. Hence, it results questionable the existence of an unique model that could properly describe the variety of cuprate superconductors, as the two-dimensional t-t'-U model was thought to be.