Coexistence of Superconductivity and Superionicity in Li$_2$MgH$_{16}$

TL;DR

This study demonstrates that Li$_2$MgH$_{16}$ exhibits both high-temperature superconductivity and superionic behavior simultaneously, with quantum effects significantly influencing the superconducting transition temperature.

Contribution

It introduces a first-principles, non-perturbative approach to analyze superconductivity in superionic materials, revealing the coexistence of superconductivity and superionicity in Li$_2$MgH$_{16}$.

Findings

Superconductivity with $T_c$ of 277 K at 260 GPa.

Quantum diffusion and anharmonic vibrations reduce $T_c$ from 473 K.

Superconductivity and superionicity coexist in Li$_2$MgH$_{16}$.

Abstract

We study superconductivity in the superionic phase of the clathrate hydride Li$_2$MgH$_{16}$, where hydrogen ions diffuse among the lattice formed by lithium and magnesium ions. By employing the stochastic path-integral approach, we non-perturbatively take into account the effects of quantum diffusion and anharmonic vibrations. Our calculations reveal strong electron-ion coupling ($\lambda(0)$ = 3.7) and a high superconducting transition temperature ($T_c$) of 277 K under 260 GPa, at which the material is still superionic. $T_c$ is significantly suppressed compared with the result $T_c$ = 473 K obtained from the conventional approach based on the harmonic approximation. Our study, based on a first-principles approach applicable to superionic systems, indicates that the superconductivity and superionicity can coexist in Li$_2$MgH$_{16}$.