Classifying charge carrier interaction in highly-compressed elements and silane

TL;DR

This paper investigates the charge carrier interactions in highly-compressed superconductors, revealing dominance of non-electron-phonon mechanisms, challenging the electron-phonon pairing assumption and suggesting alternative mechanisms should be explored.

Contribution

It demonstrates that non-electron-phonon interactions dominate in several high-pressure superconductors, contradicting previous electron-phonon based theories.

Findings

Non-electron-phonon interactions dominate in studied materials.

Failure of electron-phonon based predictions for high Tc.

Alternative pairing mechanisms should be considered.

Abstract

Since pivotal experimental discovery of the near-room-temperature superconductivity (NRTS) in highly-compressed sulphur hydride by Drozdov et al (2015 Nature 525 73-76), more than a dozen of binary and of ternary hydrogen-rich phases exhibited superconducting transition above 100 K have been discovered to date. There is a widely accepted theoretical point of view that primary mechanism governing the emergence of superconductivity in hydrogen-rich phases is the electron-phonon pairing. However, our recent analysis of experimental temperature dependent resistance in $H_{3}S$, $LaH_{x}$, $PrH_{9}$ and $BaH_{12}$ (arXiv: 2104.14145) showed that these compounds exhibit the dominance of non-electron-phonon charge carrier interaction and, thus, it is unlikely that the electron-phonon pairing is the primary mechanism for the emergence of superconductivity in these materials. Here we use the same approach to reveal charge carrier interaction in highly-compressed lithium, black phosphorous, sulfur, and silane. We found that all these superconductors exhibit the dominance of non-electron-phonon charge carrier interaction. This explains the failure of high-Tc values predicted for these materials by the first-principles calculations which utilized the electron-phonon pairing as the mechanism for the emergence of superconductivity in these materials. Our result implies that alternative pairing mechanisms (i.e., electron-magnon, electron-polaron, electron-electron, etc.) should be tested within first-principles calculations approach as possible mechanisms for the emergence of superconductivity in highly-compressed superconductors.