Superconductivity close to the charge-density-wave instability

TL;DR

This paper investigates how charge-density-wave and s-wave superconducting orders compete and coexist in a quasi-one-dimensional electron-phonon system, revealing a power-law relation between superconducting transition temperature and phonon frequency near a quantum critical point.

Contribution

It provides a detailed phase diagram of competing orders using weak coupling RG, highlighting the power-law dependence of Tc on phonon frequency near a CDW quantum critical point.

Findings

Superconducting Tc scales as ω_D^{0.7} near the quantum critical point.

Charge-density-wave and superconducting orders can coexist depending on nesting deviations.

Coulomb interactions influence the stability of the competing phases.

Abstract

We use the weak coupling renormalization group method to examine the interplay between charge-density-wave and s-wave superconducting orders in a quasi-one-dimensional model of electrons interacting with acoustic phonons. The relative stability of both types of order is mapped out at arbitrary nesting deviations and Debye phonon frequency $\omega_D$. We singled out a power law increase of the superconducting $T_c\sim \omega_D^{0.7}$ from a quantum critical point of charge-density-wave order triggered by nesting alterations. The results capture the key features shown by the proximity between the two types of ordering in the phase diagram of the recently discovered Perylene based organic superconductor under pressure. The impact of Coulomb interaction on the relative stability of the competing phases is examined and discussed in connection with the occurrence of s-wave superconductivity in low dimensional charge-density-wave materials.