Stability and Superconductivity of Ternary Polyhydrides

Abstract

We review five years of experimental and theoretical attempts (2020-2025) to enhance the superconducting critical temperature ($\textit{T$_c$}$) of hydrogen-rich compounds by alloying binary superhydrides with additional elements. Despite predictions of higher $\textit{T$_c$}$ in ternary systems such as La-Y-H, La-Ce-H, and Ca-Mg-H, experiments consistently show that the maximum $\textit{T$_c$}$ in disordered ternary superhydrides does not exceed that of the best binary parent hydrides within experimental uncertainty. Instead, alloying primarily stabilizes high-symmetry polyhydride phases at lower pressures, enabling $\textit{T$_c$}$ = 200 K near 110-120 GPa, while also improving vortex pinning and upper critical fields. Magnetic dopants suppress $\textit{T$_c$}$, whereas nonmagnetic additives leave it nearly unchanged, reminiscent of Anderson's theorem. These findings indicate that alloying is unlikely to raise $\textit{T$_c$}$, but can reduce the pressures required to stabilize high-$\textit{T$_c$}$ phases. We propose that fully ordered ternary hydrides, synthesized via controlled hydrogenation of intermetallic precursors, offer a promising route toward this goal. One of the most promising compounds of this kind is the recently discovered LaSc${}_2$H${}_{24}$.

References in corpus (15)

• Conventional superconductivity at 203 K at high pressures
• Anomalous high-temperature superconductivity in YH${}_6$
• Superconductivity at 161 K in Thorium Hydride $Th{H}_{10}$: Synthesis and Properties
• Superconductivity at 253 K in lanthanum-yttrium ternary hydrides
• High-Temperature Superconductivity in Cerium Superhydrides
• Superconductivity in sodalite-like yttrium hydride clathrates
• Effect of paramagnetic impurities on superconductivity in polyhydrides: $\text{s}$-wave order parameter in Nd-doped LaH${}_{10}$
• Non-Fermi-Liquid Behavior of Superconducting SnH${}_4$
• (La,Th)H${}_{10}$: the potential high-$T_c$ superconductors stabilized thermodynamically below 200 GPa
• Prediction of Room-Temperature Superconductivity in Quasi-atomic H2-Type Hydrides at High Pressure
• Vortex phase dynamics in yttrium superhydride YH${}_6$ at megabar pressures
• IsoME: Streamlining High-Precision Eliashberg Calculations
• Ab initio modeling of superconducting alloys
• Fundamental limits on the electron-phonon coupling and superconducting $T_c$
• Ternary superhydrides under pressure of Anderson's theorem: Near-record superconductivity in (La,Sc)H${}_{12}$

Cited by in corpus (1)

• Transmission of radio-frequency waves and nuclear magnetic resonance in lanthanum superhydrides