Enhancement of the superconducting transition temperature from the competition between electron-electron correlations and electron-phonon interactions

TL;DR

This paper reveals that the interplay between electron-electron correlations and electron-phonon interactions can dramatically increase the superconducting transition temperature, suggesting a universal mechanism affecting various Fermi surface instabilities.

Contribution

It introduces a renormalization group analysis showing a universal enhancement mechanism for superconductivity and other Fermi surface instabilities due to competing interactions.

Findings

Superconducting transition temperature can exceed 200 K due to interaction competition.

The enhancement mechanism is applicable to various Fermi surface instabilities.

The universal structure is similar to that of Kondo temperature enhancement with Rashba spin-orbit interactions.

Abstract

We uncover that the competition between electron-electron correlations and electron-phonon interactions gives rise to unexpectedly huge enhancement of the superconducting transition temperature, several hundreds percent larger ($\geq$ 200 K) than that of the case when only one of the two is taken into account ($\sim$ 30 K). Our renormalization group analysis claims that this mechanism for the enhancement of the critical temperature is not limited on superconductivity but applied to various Fermi surface instabilities, proposing an underlying universal structure, which turns out to be essentially identical to that of a recent study [Phys. Rev. Lett. {\bf 108}, 046601 (2012)] on the enhancement of the Kondo temperature in the presence of Rashba spin-orbit interactions. We also discuss the stability of superconductivity against nonmagnetic randomness.