Superconductivity in hexagonal Ce_0.5La_0.5H₉ under high pressure.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Chemistry

Background:

• Ternary rare-earth clathrate hydrides, such as (Ce,La)H9, have shown high critical temperature (Tc) superconductivity under high pressure (90-170 GPa).
• Experimental synthesis of (Ce,La)H9 has been achieved, but its precise crystal structure and superconducting properties require further theoretical investigation.

Purpose of the Study:

• To theoretically investigate the structural stability and superconductivity of a simplified hydride alloy, Ce0.5La0.5H9.
• To determine the theoretical crystal structure and identify the conditions for strong electron-phonon coupling (EPC) in Ce0.5La0.5H9.
• To predict the critical temperature (Tc) of superconductivity for Ce0.5La0.5H9.

Main Methods:

• Density Functional Theory (DFT) calculations were employed to analyze lattice dynamical stability.
• The electron-phonon coupling (EPC) strength was calculated using the superconducting spectral function.
• The Allen-Dynes-modified McMillan equation was used to estimate the critical temperature (Tc).

Main Results:

• The theoretical crystal structure of Ce0.5La0.5H9 was determined, resolving experimental ambiguities.
• Ce0.5La0.5H9 exhibits structural stability in the pressure range of 100-150 GPa, with stability observed at 110 GPa.
• Strong electron-phonon coupling was found at 120 GPa, leading to a predicted superconducting critical temperature (Tc) of approximately 127 K.

Conclusions:

• Ce0.5La0.5H9 is a theoretically stable hydride alloy with significant potential for high-temperature superconductivity.
• The study provides a theoretical framework for understanding the superconducting mechanisms in rare-earth clathrate hydrides.
• The predicted Tc of 127 K highlights Ce0.5La0.5H9 as a promising candidate for future experimental exploration in the field of superconductivity.