Development of Density-Functional Theory for Plasmon-Assisted Superconducting State: Application to Lithium Under High Pressures

TL;DR

This paper extends density-functional theory for superconductors to include plasmon effects, improving predictions of superconducting transition temperatures in high-pressure lithium and enabling non-empirical studies of unconventional superconductivity.

Contribution

The authors develop a new exchange-correlation kernel in SCDFT that accounts for dynamical Coulomb interactions, incorporating plasmons for more accurate Tc predictions.

Findings

Higher Tc predictions for lithium under high pressure with plasmon inclusion

Improved agreement between calculated and experimental Tc values

Demonstration of the formalism's potential for studying unconventional superconductivity

Abstract

We extend the density-functional theory for superconductors (SCDFT) to take account of the dynamical structure of the screened Coulomb interaction. We construct an exchange-correlation kernel in the SCDFT gap equation on the basis of the random-phase approximation, where electronic collective excitations such as plasmons are properly treated. Through an application to fcc lithium under high pressures, we demonstrate that our new kernel gives higher transition temperatures (Tc) when the plasmon and phonon cooperatively mediate pairing and it improves the agreement between the calculated and experimentally observed Tc. The present formalism opens the door to non-empirical studies on unconventional electron mechanisms of superconductivity based on density functional theory.