| Summary: | Recent reports of the superconductivity in hydrides of two different families (covalent
lattice, as in SH3 and clathrate-type H-cages containing La and Y atoms, as in
LaH10 and YH6) have revealed new families of high-Tc
materials with Tc’s near room temperature values. These findings confirm
earlier expectations that hydrides may have very high Tc’s due to the fact that
light H atoms have very high vibrational frequencies, leading to high Tc values
within the conventional Bardeen–Cooper–Schrieffer phonon mechanism of superconductivity.
However, as is pointed out by Ashcroft, it is important to have the metallic hydrogen
“alloyed” with the elements added to it. This concept of a metallic alloy containing a
high concentration of metal-like hydrogen atoms has been instrumental in finding new
high-Tc superhydrides. These new superhydride “room-temperature”
superconductors are stabilized only at very high pressures above 100 GPa, making the
experimental search for their superconducting properties very difficult. We will review
the current experimental and theoretical results for LaH10−x and
YH6−x superhydrides.
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