The electron–phonon coupling constant and the Debye temperature in polyhydrides of thorium, hexadeuteride of yttrium, and metallic hydrogen phase III

Milestone experimental discovery of superconductivity above 200 K in highly-compressed sulphur hydride by Drozdov (Nature 525, 73 (2015)) sparked and theoretical investigations metallic hydrides. Since then, a dozen superconducting binary ternary polyhydrides have been discovered. For instance, there are three thorium: Th4H15, ThH9, ThH10 four yttrium: YH4, YH6, YH7, YH9. In addition to hydrogen-based compounds, recently Eremets (arXiv:2109.11104) reported on the metallization hydrogen, which exhibits phase transition into hydrogen III at P>330 GPa T<200 K. Here we analyzed temperature-dependent resistance, R(T), thorium, hexadeuteride yttrium deduced Debye temperature, $T$$_{\theta}$, electron-phonon coupling constant, $\lambda_{e-ph}$, for these conductors. We found that Th4H15 $\lambda_{e-ph}$ = 0.82-0.99 is very good agreement with value 0.84 from heat capacity measurements (Miller, Phys. Rev. B 14, 2795 (1976)). P63/mmc-ThH9 (P 170 GPa) $\lambda_{e-ph}$(170 1.46, reasonable Semenok (Materials Today 33, 36 (2020)). Deduced 1.70 Fm-3m-ThH10 remarkable first-principles calculated $\lambda_{e-ph}$(174 GPa)=1.75 (Semenok, Materials $\lambda_{e-ph}$(172 1.90 Im-3m-YD6 also excellent $\lambda_{e-ph}$(165 GPa)=1.80 (Troyan, Advanced 2006832 (2021)). And finally, $T$$_{\theta}$(402 727 implies $\lambda_{e-ph}$(402 GPa)<1.7 this metal.