Electron pairing in the Hubbard model as a result of on-site repulsion fluctuations

TL;DR

This paper investigates how fluctuations in on-site Coulomb repulsion within the Hubbard model can induce electron pairing, potentially leading to a stable paired state in insulating systems across various lattice structures.

Contribution

It introduces a novel pairing mechanism driven by on-site repulsion fluctuations, expanding understanding of electron pairing beyond traditional attractive interactions.

Findings

Identifies conditions for stable electron pairing due to Coulomb fluctuations

Calculates critical values of Coulomb repulsion and fluctuations for pairing stability

Applies analysis to chain, square, and cubic lattice structures

Abstract

We focus our quantitative analysis on the stability of the insulator state in the Hubbard model at a half-filling. Taking into account large-scale fluctuations (with a long relaxation time) of the on-site Coulomb repulsion, we consider the possibility of realizing a stabile state which is characterized by pairing for electrons. The pairing mechanism is as follows: due to fluctuations of on-site repulsion of electrons, holes, as excited states, are formed electron pairs. The bare values of on-site Coulomb repulsion and its fluctuations, for which the states with electron pairing are stable, are calculated. The proposed pairing mechanism is to some extent similar to the formation of a localized moment in the Wolf model. The calculations were performed for the chain, as well as square and cubic lattices.