Why Mercury is a superconductor

TL;DR

This paper investigates the superconducting properties of solid mercury using advanced computational methods, revealing anomalies in electronic and lattice behaviors that influence its critical temperature.

Contribution

It provides the first detailed computational analysis of mercury's superconductivity, highlighting the roles of correlations, spin-orbit coupling, and semicore levels.

Findings

Electron-electron correlations affect structural properties.

Spin-orbit coupling influences dynamical stability.

Semicore d levels impact Coulomb interaction and Tc.

Abstract

Despite being the oldest known superconductor, solid mercury is mysteriously absent from all current computational databases of superconductors. In this work, we present a critical study of its superconducting properties based on state-of-the-art superconducting density-functional theory. Our calculations reveal numerous anomalies in electronic and lattice properties, which can mostly be handled, with due care, by modern ab-initio techniques. In particular, we highlight an anomalous role of (i) electron-electron correlations on structural properties (ii) spin-orbit coupling on the dynamical stability, and (iii) semicore $d$ levels on the effective Coulomb interaction and, ultimately, the critical temperature.