  Superconductivity in highly-pressurized hydrides became primary direction for
the exploration of fundamental upper limit for the superconducting transition
temperature, Tc, after Drozdov et al (Nature 2015, 525, 73) discovered
superconducting state with $T_c=203 K$ in highly-compressed sulphur hydride. To
date several dozens of high-temperature superconducting polyhydrides have been
discovered. In addition, recently, it was reported that highly-compressed
titanium and scandium exhibit record-high $T_c$ (up to 36 K), which is by
manifold exceeded $T_c=9.2 K$ of niobium, which is the record high-$T_c$
ambient pressure metallic superconductor. Here we analysed experimental data on
for recently discovered high-pressure superconductors (which exhibit high
transition temperatures within their classes): elemental titanium (Zhang et al,
Nature Communications 2022; Liu et al, Phys. Rev. B 2022), $TaH_3$ (He et al,
Chinese Phys. Lett. 2023), $LaBeH_8$ (Song et al, Phys. Rev. Lett. 2023), and
black (Li et al, Proc. Natl. Acad. Sci. 2018) and violet (Wu et al, arXiv 2023)
phosphorous, to reveal the nonadiabaticity strength constant, $T_{\theta}/T_F$
(where $T_{\theta}$ is the Debye temperature, and $T_F$ the Fermi temperature)
in these superconductors. The analysis showed that ${\delta}$-phase of titanium
and black phosphorous exhibit the $T_{\theta}/T_F$ which are nearly identical
to ones associated in A15 superconductors, while studied hydrides and violet
phosphorous exhibit the constants in the same ballpark with $H_3S$ and
$LaH_{10}$.

Superconductivity