Comment on "Coexistence of superconductivity and topological aspects in beryllenes", Materials Today Physics 38, 101257 (2023)

TL;DR

This paper critically examines previous claims about beryllene's superconductivity and topological properties, finding weaker superconducting evidence and clarifying the coexistence of topological states with superconductivity.

Contribution

It challenges prior predictions of high-temperature superconductivity in beryllene and clarifies the coexistence of topological states with superconductivity.

Findings

Superconducting properties of beryllene are weaker than previously reported.

The temperature dependence of the superconducting gap shows unphysical trends.

Topological states coexist with superconductivity in beryllene.

Abstract

In a recent publication by Li $\textit{et al.}$, two phases of beryllene - $\alpha$ and $\beta$ - were predicted to be single-gap superconductors with critical temperatures of 9.9 K and 12.6 K respectively. Moreover, the $\alpha$-beryllene was shown to host type-I Dirac fermions with the existence of nontrivial edge states. We observe significantly weaker superconducting properties of both beryllene configurations. We argue that the superconducting gap evolution with temperature, as shown in Figure 5 (b and d) of Li $\textit{et al.}$, exhibits clearly unphysical trends with increasing temperature, leading to significantly overestimated values of the critical temperature and erroneous conclusions concerning the two-gap superconducting nature of $\beta$-beryllene. On a positive note, we report the value of the gap in the Dirac cone of the topological states of interest that exceeds the temperature range of superconductivity in $\alpha$-beryllene, supporting the coexistence of topological features and superconductivity in this material.