Is MgB$_2$ a superconductor?

TL;DR

This paper critically examines claims about hydrogen-rich compounds and argues that MgB$_2$ is not a superconductor based on model analysis and experimental data interpretation.

Contribution

It challenges previous assertions by applying the Hirsch-Marsiglio model to MgB$_2$, demonstrating it does not exhibit superconductivity.

Findings

MgB$_2$ is not a superconductor according to the model.

Previous claims about hydrides' superconductivity are based on flawed data analysis.

The application of the model reveals inconsistencies in earlier interpretations.

Abstract

Hirsch and Marsiglio, in their recent publication (J. Supercond. Nov. Mag. 35, 3141-3145 (2022)), assert that experimental data on the trapping of magnetic flux by hydrogen-rich compounds clearly demonstrate the absence of superconductivity in hydrides at high pressures. We argue that this assertion is incorrect, as it relies on the wrong model coupled with selective manipulations (hide/delete) of calculated datasets and ignores the reference measurements after the release of pressure. A critical examination of the authors' claim of having performed fitting of experimental data to the model reveals that, in fact, the authors conducted simulations where all free parameters were fixed. Importantly, an application of the Hirsch-Marsiglio model to MgB$_2$ leads to the conclusion that it is not a superconductor.