Superconducting ternary hydrides: progress and challenges

Abstract

Since the discovery of high-temperature superconductors H3S and LaH10 under high pressure, compressed hydrides have received extensive attention as promising candidates for room temperature superconductors. As the results of current high-pressure theoretical and experiments studies, almost all the binary hydrides with high superconducting transition temperature (Tc) require extremely high pressure to remain stable, hindering any practical applications. In order to further lower the stable pressure and improve the superconductivity, researchers started exploring ternary hydrides and have made many achievements in recent years. Here, we discuss recent progress in ternary hydrides, aiming to deepen the understanding of the key factors regulating the structural stability and superconductivity of ternary hydrides, such as structural motifs, bonding features, electronic structure, electron-phonon coupling etc. Furthermore, the current issues and challenges of superconducting ternary hydrides are presented, together with the prospects and opportunities for future research.

Layered Hydride LiH4 with a Pressure-Insensitive Superconductivity

“…Since the discovery of near-room-temperature superconductivity in H 3 S and LaH 10 , , the search for hydrides has been a hot topic in chemistry, materials science, and condensed matter physics. − To date, many high- T c hydrides have been proposed at high pressures, and they share a common feature, namely, superconductivity dominated by covalent H-based structural units. , For example, one-dimensional (1D) H 7 chain in C 222 1 GaH 7 , H nanotube in P 6 3 / m HfH 9 , 2D H layer consisting of H 5 pentagons in P 6 3 / mmc HfH 10 , 3D H cage in Im 3̅ m CaH 6 , and 3D H-based alloy framework in Fm 3̅ m LaBeH 8 . The stability of these units is inextricably linked to the charge transfer from metal atoms to the antibonding orbitals of the H–H bonds.…”

The preface: Toward higher-Tc superconductivity under lower pressure—from binary to ternary superhydrides

“…The other review paper by W. Zhao et al. [ 7 ] summarizes recent progress in ternary hydrides, which have richer chemical compositions and structural prototypes than binary hydrides, and hence may host more novel properties with the possibility of high T c at lower pressures. The issues and challenges of ternary hydrides are also presented together with the prospects and opportunities of this class of hydrides.…”