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

TL;DR

This paper introduces a novel three-pole approximation within the Composite Operator Method to analyze the 2D Hubbard model, revealing new insights into the pseudogap behavior in underdoped cuprates.

Contribution

The study develops a new three-pole approximation including spin fluctuation effects, providing a deeper understanding of single-particle properties in the strongly correlated regime.

Findings

Unusual behavior of the van Hove singularity observed

Identification of a precursor to the pseudogap regime

Enhanced understanding of Fermi surface anomalies

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 properties of the underdoped cuprates, we include in the operatorial basis, together with the usual Hubbard operators, a field describing the electronic transitions dressed by the nearest-neighbor spin fluctuations, which play a crucial role in the unconventional behavior of the Fermi surface and of the electronic dispersion. Then, we adopt this approximation to study the single-particle properties in the strong coupling regime and find an unexpected behavior of the van Hove singularity that can be seen as a precursor of a pseudogap regime.