Superconductivity above 200 K Observed in Superhydrides of Calcium

TL;DR

This paper reports the experimental discovery of calcium superhydrides exhibiting superconductivity above 210 K at high pressures, marking a significant step toward room-temperature superconductivity.

Contribution

It provides the first experimental evidence of calcium superhydrides with Tc above 200 K, expanding the family of high-temperature superconductors.

Findings

Superconductivity observed above 210 K in calcium superhydrides.

Synthesized at 160-190 GPa and ~2000 K using diamond anvil cell.

Estimated upper critical field Hc(0) ~ 268 T.

Abstract

Searching for superconductivity with Tc near room temperature is of great interest both for fundamental science & many potential applications. Here we report the experimental discovery of superconductivity with maximum critical temperature (Tc) above 210 K in calcium superhydrides, the new alkali earth hydrides experimentally showing superconductivity above 200 K in addition to sulfur hydride & rare-earth hydride system. The materials are synthesized at the synergetic conditions of 160~190 GPa and ~2000 K using diamond anvil cell combined with in-situ laser heating technique. The superconductivity was studied through in-situ high pressure electric conductance measurements in an applied magnetic field for the sample quenched from high temperature while maintained at high pressures. The upper critical field Hc(0) was estimated to be ~268 T while the GL coherent length is ~11 angstrom. The in-situ synchrotron X-ray diffraction measurements suggest that the synthesized calcium hydrides are primarily composed of CaH6 while there may also exist other calcium hydrides with different hydrogen contents.