Phonon mediated hole pairing in the 1D Hubbard model near half-filling

TL;DR

This study uses DMRG to explore how strong electron correlations and phonon interactions influence charge order and pairing in a 1D Hubbard model, proposing a new hole pairing mechanism relevant to high-temperature superconductors.

Contribution

It introduces a novel phonon-mediated hole pairing mechanism in the 1D Hubbard model near half-filling, highlighting the interplay between electron correlations and electron-phonon coupling.

Findings

Strong electron correlations suppress charge order.

Extended polarons form in strong electron-phonon coupling regime.

Two polarons can pair via phonon-mediated charge fluctuations.

Abstract

The Hamiltonian describing a system of strongly correlated electrons coupled to dispersionless phonons was solved numerically for a ring of 8 atoms using the density matrix renormalization group (DMRG) method. It was found that electron correlation and electron-phonon coupling compete against each other, and strong electron correlations suppress the charge-ordered insulating state. This allows extended polarons to form in the strong electron-phonon coupling regime. It is shown that in this regime two polarons may form a pair via phonon mediated charge-fluctuation interaction. Based on the results we propose a novel mechanism of hole pairing. This mechanism could be relevant to High-Tc cuprates.