Physical origin of the sharp Tc drop at low hydrogen-projected DOS

Determine whether the observed sharp drop in superconducting critical temperature when the fraction of the density of states at the Fermi level attributed to hydrogen atoms falls below 0.2 is physically meaningful or an artifact caused by limited data or the projection methodology used to assign hydrogen contributions to the density of states.

Background

A correlation between the superconducting critical temperature (Tc) and the hydrogen contribution to the density of states at the Fermi level (H_DOS) has been noted for binary hydrides and appears to persist in ternaries. The dataset shows a pronounced decline in Tc below H_DOS ≈ 0.2.

However, the authors explicitly state uncertainty about the origin of this drop—whether it reflects genuine physics or arises from data scarcity or projection artifacts in assigning hydrogen weights to the DOS. Establishing the cause is essential for using H_DOS thresholds in predictive models.

References

Additionally, it is noteworthy that below a value of 0.2, there is a sharp drop in c. This behavior was first observed in binary hydrides and continues to hold for ternary systems, yet it is unclear if this drop presents a physical meaning, or if it is an artifact due to lack of data or projection artifact onto {DOS}.

— Refining Tc Prediction in Hydrides via Symbolic-Regression-Enhanced Electron-Localization-Function-Based Descriptors (2506.17456 - Belli et al., 20 Jun 2025) in Results, Subsection "Networking and Superconductivity"