Structural, electronic, vibrational, and superconducting properties of hydrogenated chlorine

Comparison of highly-compressedC2/m-SnH12superhydride with conventional superconductors

Satterthwaite and Toepke (1970Phys. Rev. Lett.25741) predicted high-temperature superconductivity in hydrogen-rich metallic alloys, based on an idea that these compounds should exhibit high Debye frequency of the proton lattice, which boosts the superconducting transition temperature,T_c. The idea has got full confirmation more than four decades later when Drozdovet al(2015Nature52573) experimentally discovered near-room-temperature superconductivity in highly-compressed sulphur superhydride, H₃S. To date, more than a dozen of high-temperature hydrogen-rich superconducting phases in Ba-H, Pr-H, P-H, Pt-H, Ce-H, Th-H, S-H, Y-H, La-H, and (La, Y)-H systems have been synthesized and, recently, Honget al(2021arXiv:2101.02846) reported on the discovery ofC2/m-SnH₁₂phase with superconducting transition temperature ofT_c∼ 70 K. Here we analyse the magnetoresistance data,R(T,B), ofC2/m-SnH₁₂phase and report that this superhydride exhibits the ground state superconducting gap of Δ(0) = 9.2 ± 0.5 meV, the ratio of 2Δ(0)/k_BT_c= 3.3 ± 0.2, and 0.010 <T_c/T_F< 0.014 (whereT_Fis the Fermi temperature) and, thus,C2/m-SnH₁₂falls into unconventional superconductors band in the Uemura plot.

Superconductivity in bilayer graphene intercalated with alkali and alkaline earth metals

With the enormous research activity focused on graphene in recent years, it is not surprising that graphene superconductivity has become an attractive area of research. To date, no superconducting properties have been experimentally observed in the pristine form of graphene but controllable structure manipulation is a promising way to induce a superconducting state in graphene-based systems. Therefore, herein we investigate the possible superconductivity in two-layer graphene intercalated with atoms of alkali and alkaline earth metals. Results of our calculations conducted within the framework of density functional theory combined with the Eliashberg theory allow us to conclude that the Cooper pairing in these superconductors can be described in a standard phonon-mediated scenario. In this regime, C6XC6 (X = K, Ca, Rb and Sr) are expected to be superconductors with estimated superconducting critical temperatures of 5.47-14.56 K and with the ratios of energy gap to transition temperature exceeding the value predicted by the Bardeen-Cooper-Schrieffer theory.