High-Temperature Superconducting Phase in Clathrate Calcium Hydride CaH$_6$ up to 215 K at a Pressure of 172 GPa

The recent discovery of superconductive rare earth and actinide superhydrides has ushered in a new era of superconductivity research at high pressures. This distinct type of clathrate metal hydrides was first proposed for alkaline-earth-metal hydride CaH$_6$ that, however, has long eluded experimental synthesis, impeding an understanding of pertinent physics. Here, we report successful synthesis of CaH$_6$ and its measured superconducting critical temperature T$_c$ of 215 K at 172 GPa, which is evidenced by a sharp drop of resistivity to zero and a characteristic decrease of T$_c$ under a magnetic field up to 9 T. An estimate based on the Werthamer-Helfand-Hohenberg model gives a giant zero-temperature upper…

• SS
  Salt Science Research Foundation
• NN
  National Natural Science Foundation of China

  Awards: 12074138, 11874175, 12074139, 11874176, 12034009, 11974134, 52090024
• CA
  Chinese Academy of Sciences

  Award: XDB33000000
• OY
  Outstanding Young Talent Foundation of Jilin Province

  Award: 20190103040JH
• DE
  Deutsches Elektronen-Synchrotron
• NK
  National Key Research and Development Program of China

  Award: 2018YFA0305900
• SA
  Science and Technology Innovative Research Team in Higher Educational Institutions of Hunan Province
• BS
  Beijing Synchrotron Radiation Facility