Density-matrix renormalization group study of pairing when electron-electron and electron-phonon interactions coexist: effect of the electronic band structure

TL;DR

This study uses density-matrix renormalization group methods to explore how electron-electron and electron-phonon interactions influence pairing in the Holstein-Hubbard model, revealing lattice-dependent pairing phenomena.

Contribution

It demonstrates that pairing can emerge from coexisting interactions and depends on lattice structure, especially when electron-hole symmetry is broken.

Findings

Pairing nearly degenerate with CDW in certain regimes

Pairing becomes dominant when electron-hole symmetry is broken

Lattice structure influences pairing emergence

Abstract

Density-matrix renormalization group is used to study the pairing when both of electron-electron and electron-phonon interactions are strong in the Holstein-Hubbard model at half-filling in a region intermediate between the adiabatic (Migdal's) and antiadiabatic limits. We have found: (i) the pairing correlation obtained for a one-dimensional system is nearly degenerate with the CDW correlation in a region where the phonon-induced attraction is comparable with the electron-electron repulsion, but (ii) pairing becomes dominant when we destroy the electron-hole symmetry in a trestle lattice. This provides an instance in which pairing can arise, in a lattice-structure dependent manner, from coexisting electron-electron and electron-phonon interactions.