关键词: superconductivity, hydride, low pressures, ionized molecular groups

Abstract: The emergence of high-temperature superconductivity in hydrogen-rich compounds has opened up promising avenues for investigating unique hydrogen motifs that exhibit exceptional superconducting properties. Nevertheless, the requirement for extremely high synthesis pressures poses significant barriers to experimentally probing potential physical properties. Here, we have designed a structure wherein NH$_{3}$ tetrahedra are intercalated into the body-centered cubic lattice of Yb, resulting in the formation of Yb(NH$_{3}$)$_{4}$. Our first-principles calculations reveal that metallic behavior emerges from the ionization of sp$^{3}$-hybridized $\sigma$-bonds in NH$_{3}$, which is enabled by electron transfer from ytterbium orbitals to NH$_{3}$ anti-bonding $\sigma$-orbitals. A distinctive feature of this structure is the Fermi surface nesting, which leads to optical phonon softening and consequently enhances electron-phonon coupling. The subsequent density-functional theory (DFT) calculations demonstrate that this $I$-43$m$ phase of Yb(NH$_{3}$)$_{4}$ exhibits a superconducting critical temperature ($T_{\rm c}$) of 17.32 K under a modest pressure of 10 GPa. Our investigation presents perspectives on achieving phonon-mediated superconductivity at relatively low pressures, thereby opening up extensive possibilities for the attainment of high-temperature superconductivity in hydrogen-based superconducting systems with specific ionized molecular groups.

Key words: superconductivity, hydride, low pressures, ionized molecular groups