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

Area of Science:

• Materials Science
• Condensed Matter Physics
• Superconductivity

Background:

• Hydrogen-based superconductors offer a path to room-temperature superconductivity.
• Current limitations include extremely high pressures (e.g., 267 GPa for carbonaceous sulfur hydride) hindering practical applications.
• A key challenge is achieving superconductivity at substantially lower pressures.

Purpose of the Study:

• To propose a rational design strategy for high-temperature superconductors at low pressures.
• To explore ternary hydrogen-based superconductors with alloy backbones.
• To identify materials exhibiting high critical temperatures (T_{c}) under moderate pressures.

Main Methods:

• Computational prediction and theoretical design of novel ternary hydrogen-based compounds.
• Focus on alloying small-radius elements with hydrogen to form specific structures.
• Investigation of the 'fluorite-type' backbone (AXH_{8}) for stability and superconducting properties.

Main Results:

• Identification of the 'fluorite-type' backbone as a promising structure for high-T_{c} materials at moderate pressures.
• Prediction of LaBeH_{8} in the Fm3[over ¯]m phase as thermodynamically stable above 98 GPa and dynamically stable down to 20 GPa.
• Calculated critical temperature (T_{c}) for LaBeH_{8} is approximately 185 K, achieved at a much lower pressure than similar compounds like LaH_{10} (170 GPa).

Conclusions:

• The proposed alloying strategy enables the design of ternary H-based superconductors with improved pressure-temperature profiles.
• LaBeH_{8} represents a significant advancement, demonstrating the potential for high-T_{c} superconductivity at pressures considerably lower than previously reported.
• This work paves the way for discovering new high-T_{c} ternary hydrogen-based superconductors closer to ambient pressure conditions.