Superconducting hydrides and metallic hydrogen at megabar pressures

6 problems

• Is there a hydride superconducting above 77 K at ambient pressure

  Open

  Hydride superconductors need enormous pressure; the goal is a hydrogen-rich compound that keeps a high transition temperature, above liquid-nitrogen temperature, at normal pressure.

• Can first-principles Eliashberg theory predict hydride $T_{c}$ within ten percent

  Partially resolved

  Hydride superconductivity is thought to come from lattice vibrations, which theory can compute, but light hydrogen atoms vibrate strongly and quantum mechanically, which complicates predictions.

• Is 298 K superconductivity in compressed La-Sc-H reproducible

  Open

  A 2025 report claims that a hydrogen-rich compound of lanthanum and scandium superconducts up to about room temperature when squeezed to about 2.5 million atmospheres; independent confirmation is required.

• Do megabar hydrides show consistent bulk magnetic evidence of superconductivity

  Partially resolved

  Hydride samples are tiny and are enclosed in diamond cells, so measuring the magnetic field expulsion that defines a superconductor is hard, and some published magnetic data have been challenged.

• At what pressure does solid hydrogen become a metal

  Contested

  Theory predicted in 1935 that squeezed hydrogen becomes a metal; experiments near 4 to 5 million atmospheres claim it, but the evidence is disputed.

• Does metallic hydrogen superconduct, and at what temperature

  Open

  Because hydrogen atoms are so light their vibrations are fast, and theory predicts that metallic hydrogen could superconduct near or above room temperature.