Realizing high-temperature superconductivity in compressed molecular-hydrogen through Li doping

TL;DR

This paper demonstrates that lithium doping in compressed molecular hydrogen can induce high-temperature superconductivity above 300 K at 250 GPa by tuning hydrogen interactions and stabilizing structures, without dissociation.

Contribution

It introduces a new stable cubic LiH12 phase with high-temperature superconductivity potential under high pressure, using first-principles calculations and electron-phonon coupling analysis.

Findings

LiH12 phase shows potential for superconductivity above 300 K at 250 GPa.

Lithium doping tunes H-H distances, promoting metallization.

Low- and intermediate-energy phonons are key to strong electron-phonon coupling.

Abstract

In this study, we explore lithium-doped stable molecular hydrogen structures by performing first-principles crystal structure searches across varying compositions in the Li-H system under high pressure. Our search reveals a cubic phase of LiH12, which shows promise as a high-temperature superconductor. Our Bader charge analysis suggests that electron transfer from Li to H atoms tunes the intra- and inter-molecular H-H distances, which are critical for the metallization of molecular hydrogen. This modulation alters the interaction between bonding and anti-bonding 1s states of hydrogen molecules. Furthermore, Li ions serve as stabilizers for the distorted H2 molecular network through ionic interactions. Numerical solutions to the fully anisotropic Migdal-Eliashberg equations reveals that this phase could exhibit superconductivity above 300 K at a pressure of 250 GPa, a pressure value that is typically achievable using a diamond anvil cell. Detailed analysis of species-specific phonons and the Eliashberg function shows that low- and intermediate-energy phonons are crucial in promoting strong electron-phonon coupling. Thus, our study establishes lithium doping as a promising approach to induce high-temperature superconductivity in compressed molecular hydrogen without causing molecular dissociation.