Coexistence of superconductivity and charge-density waves in a two-dimensional Holstein model at half-filling

TL;DR

This paper investigates the competition and coexistence of superconductivity and charge-density waves in a two-dimensional Holstein model at half-filling using the projector-based renormalization method, revealing a crossover and coexistence regime.

Contribution

It introduces a detailed analysis of the coexistence of superconductivity and charge order in a 2D Holstein model using PRM, highlighting a crossover behavior.

Findings

Crossover between superconducting and charge-density wave states.

Existence of a parameter range with coexistence of both orders.

Identification of a transition influenced by electron-phonon coupling strength.

Abstract

In one dimension the coupling of electrons to phonons leads to a transition from a metallic to a Peierls distorted insulated state if the coupling exceeds a critical value. On the other hand, in two dimensions the electron-phonon interaction may also lead to the formation of Cooper pairs. This competition of superconductivity and charge order (in conjunction with a lattice distortion) is studied in this letter by means of the projector-based renormalization method (PRM). Increasing the electron-phonon interaction, we find a crossover behavior between a purely superconducting state and a charge-density wave where a well-defined parameter range of coexistence of superconductivity and lattice distortion exists.