Spectral Function of a $d-p$ Hubbard Model

Abstract

This work investigates a d-p Hubbard model by the n-pole approximation in the hole-doped regime. In particular, the spectral function $A(\omega ,\vec{k})$ is analyzed varying the filling, the local Coulomb interaction and the $d-p$ hybridization. It should be remarked that the original n-pole approximation (Phys. Rev. 184 (1969) 451) has been improved in order to include adequately the $\vec{k}$-dependence of the important correlation function $<{\vec{S}}_j\cdot {\vec{S}}_i>$ present in the poles of the Green's functions. It has been verified that the topology of the Fermi surface (defined by $A(\omega =0,\vec{k})$) is deeply affected by the doping, the strength of the Coulomb interaction and also by the hybridization. Particularly, in the underdoped regime, the spectral function $A(\omega =0,\vec{k})$ presents very low intensity close to the anti-nodal points $(0,\pm \pi )$ and $(\pm \pi ,0)$. Such a behavior produces an anomalous Fermi surface (pockets) with pseudogaps in the region of the anti-nodal points. On the other hand, if the $d-p$ hybridization is enhanced sufficiently, such pseudogaps vanish. It is precisely the correlation function $<{\vec{S}}_j\cdot {\vec{S}}_i>$ present in the poles of the Green's functions which plays the important role in the underdoped situation. In fact, antiferromagnetic correlations coming from $<{\vec{S}}_j\cdot {\vec{S}}_i>$ strongly modify the quasi-particle band structure. This is the ultimate source of anomalies in the Fermi surface in the present approach.

Accepted for the publication in Int. J. of Modern Phys. B

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Cited by in corpus (5)

• Effects of a k-dependent Hybridization on the Fermi Surface of an Extended $d-p$ Hubbard Model
• The interplay between a pseudogap and superconductivity in a two-dimensional Hubbard model
• Interplay between the charge density wave phase and a pseudogap under antiferromagnetic correlations
• Specific heat of a non-local attractive Hubbard model
• Interplay between condensation energy, pseudogap and the specific heat of a Hubbard model in a n-pole approximation