[22a-A302-1~8] 11.1 Fundamental properties

▲ [22a-A302-4] Potential high-T_c superconductivity in YCeH₂₀ and LaCeH₂₀ under pressure

〇HOU SOU¹, Kousuke Nakano¹, Kenta Hongo², Ryo Maezono¹ (1.Inf. Sci. JAIST, 2.RCACI. JAIST)

Keywords:superconductor, electron-phonon coupling, superconducting hydride

Lanthanum, yttrium, and cerium hydrides are the three most well-known superconducting binary hydrides, which have gained great attention in both theoretical and experimental studies. Recent studies have shown that ternary hydrides composed of lanthanum and yttrium can achieve high superconductivity around 253 K. In this study, we employ the evolutionary-algorithm-based crystal structure prediction (CSP) method and first-principles calculations to investigate the stability and superconductivity of ternary hydrides composed of (Y, Ce) and (La, Ce) under high pressure. Our calculations show that there are multiple stable phases in Y-Ce-H and La-Ce-H hydrides, among which P4/mmm-YCeH₈, P4/mmm- LaCeH₈, R-3m-YCeH₂₀, and R-3m-LaCeH₂₀ possessing H₁₈ or H₃₂ clathrate structures can maintain both of the thermodynamic and dynamic stabilities. In addition, we also find that these phases also maintain a strong resistance to decomposition at high temperatures. Electron-phonon coupling calculations show that all of these four phases can exhibit high-temperature superconductivity. R-3m-YCeH₂₀ is predicted to have a superconducting transition temperature (T_c) as high as 246 K at 350 GPa. The T_c value of R-3m-LaCeH₂₀ at 250 GPa is about 233 K, which is slightly smaller than that of R-3m- YCeH₂₀. However, it is found that R-3m-LaCeH₂₀ can be stabilized at 200 GPa, making the high-pressure synthesis of LaCeH₂₀ easier.