Superconductivity at ~70 K in Tin Hydride SnHx under High Pressure
Various tin hydrides SnHx (x 4, 8, 12, 14) have been theoretically predicted to be stable at high pressures and to show high critical temperature superconductivity with Tc ranging from about 70 to 100 K. However, experimental verifications for any of these phases are still lacking to date. Here, we report on the in situ synthesis, electrical resistance, and synchrotron x ray diffraction measurements of SnHx at 200 GPa. The main phase of the obtained sample can be indexed with the monoclinic C2/m SnH12 via comparison with the theoretical structural modes. A sudden drop of resistance and the systematic downward shift under external magnetic fields signals the occurrence of superconductivity in SnHx at Tc 70 K with an upper critical field m0Hc2(0) 11.2 T, which is relatively low in comparison with other reported high Tc superhydrides. Various characteristic superconducting parameters are estimated based on the BCS theory.