Phase Diagram of the Holstein-Hubbard Two-Leg Ladder

TL;DR

This paper uses a functional renormalization group approach to map the phase diagram of the Holstein-Hubbard two-leg ladder, revealing that electron-phonon interactions can dominate due to retardation effects, contrasting with previous weak coupling results.

Contribution

It introduces a renormalization group method capable of analyzing both weak and strong electron-phonon couplings in the Holstein-Hubbard ladder system.

Findings

Electron-phonon interactions can dominate over electron-electron interactions.

Retardation effects significantly influence the phase diagram.

Contrasts with conventional weak coupling studies.

Abstract

Using a functional renormalization group method, we obtain the phase diagram of the two-leg ladder system within the Holstein-Hubbard model, which includes both electron-electron and electron-phonon interactions. Our renormalization group technique allows us to analyze the problem for both weak and strong electron-phonon coupling. We show that, in contrast results from conventional weak coupling studies, electron-phonon interactions can dominate electron-electron interactions because of retardation effects.