Design Principles for High Temperature Superconductors with Hydrogen-based Alloy Backbone at Moderate Pressure

Abstract

Hydrogen-based superconductors provide a route to the long-sought goal of room-temperature superconductivity, but the high pressures required to metallize these materials limit their immediate application. For example, carbonaceous sulfur hydride, the first room-temperature superconductor, can reach a critical temperature (Tc) of 288 K only at the extreme pressure of 267 GPa. The next recognized challenge is the realization of room-temperature superconductivity at significantly lower pressures. Here, we propose a strategy for the rational design of high-temperature superconductors at low pressures by alloying small-radius elements and hydrogen to form ternary hydride superconductors with alloy backbones. We identify a hitherto unknown fluorite-type backbone in compositions of the form AXH8, which exhibit high temperature superconductivity at moderate pressures. The Fm-3m phase of LaBeH8, with a fluorite-type H-Be alloy backbone, is predicted to be metastable and superconducting with a Tc ~ 191 K at 50 GPa; a substantially lower pressure than that required by the geometrically similar clathrate hydride LaH10 (170 GPa). Our approach paves the way for finding high-Tc ternary hydride superconductors at conditions close to ambient pressures.

11 pages, 4 figures

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• Metal Borohydrides as high-$T_c$ ambient pressure superconductors
• Quantum lattice dynamics and their importance in ternary superhydride clathrates
• Pressure-induced high-temperature superconductivity in ternary Y-Zr-H compounds
• Stabilizing a hydrogen-rich superconductor at 1 GPa by the charge-transfer modulated virtual high-pressure effect
• Machine-learning approach for discovery of conventional superconductors
• Quantifying the nonadiabaticity strength constant in recently discovered highly-compressed superconductors
• Stability and distortion of fcc-LaH${}_{10}$ with path-integral molecular dynamics
• Quantum Phase Transitions in a Model Hamiltonian Exhibiting Entangled Simultaneous Fermion-Pair and Exciton Condensations