Superconductivity in sodium-hydrogen-C60 ternary compound

Three Components Organic Superconductors: Intercalation of KH into C60

“…We prepared "ve compounds with the initial composition of (NaH) \V (KH) V C (x"0.1, 0.5, 1, 2, 3) by heating at 2803C for 5 h. Table 2 summarizes ESR properties (g-value and H at room temperature) and SC properties (¹ A and < 1! ) for the compounds with x"0.1, 0.5, 1, 2, and 3 of (NaH) \V (KH) V C including the reported data of -(NaH) C as x"0 (20). The ESR and SC properties of several samples prepared for each compound were quite reproducible.…”

Recovery and Enhancement of Superconductivity in the Sodium−Hydrogen−C60Ternary System

“…We know that the β-phase reveals a phase transition around 260 K from ESR and NMR measurements. 13,14 According to our preliminary low-temperature PXD study, the β-phase has a simple cubic (Pa3 h) structure below the critical temperature in which C 60 molecules are ordered, suggesting a decrease of the total entropy. 15 Thus, the simple cubic phase will be energetically lower than the fcc phase so that the β-to-R change occurs more easily on low-temperature pumping because of the reduced energy difference between the simple cubic β-phase and the orthorhombic R-phase.…”

Superconducting ternary hydrides under high pressure

“…Doping-induced superconducting transition from insulating binary hydrides mainly focuses on the alkali-metal hydrides, CH 4 , Cmcm BH 2 , and H 2 O. In early experiment, NaH is inserted into C 60 forming a nominal composition (NaH) 4 C 60 , exhibiting superconductivity at 15 K. 38,39 Recently, insulating alkali-metal hydrides (LiH, NaH, and KH) with Fm-3m symmetry are doped with alkali-earth metals (Be, Mg, and Ca), introducing extra electrons to break the original formal ionic bonds. Thus, they are transformed to be metallicity and show superconductivity in the range of 2.1-50 K (Figure 7b).…”

“…Thus they, especially with H‐rich stoichiometry, also have potential to exhibit strong EPC, which make them an appealing contender for superconductors. In fact, superconducting ternary hydrides (STHs) have been studied such as NaH‐inserted C 60 with the nominal composition (NaH) 4 C 60 38,39 and pressure‐metallized BaReH 9 40 . But they demonstrate low T c values less than 15 K, which is attributed to the filled close‐shell electron configuration in formal ionic compounds (Na + H − , and Ba 2+ [ReH 9 ] 2− ) as well as low H content for the former and H 2 molecules for the latter under high pressure 41 .…”