Reacción a "Reactions: A study still pending review announces the first superconductor at room temperature and pressure"

The discovery of a superconductor at room temperature and pressure is one of the greatest achievements that could be expected, even if its usefulness in real applications might depend on the characteristics of such a superconductor.  

The search for high-temperature superconductors has historically been fraught with false positives, including article retractions, which makes us especially wary of any discovery of a new high-temperature superconductor. Any claim of such a discovery must be accompanied by very robust measurements and careful data handling. This week two papers have appeared in the arXiv preprints database (2307.12008 and 2307.12037) claiming to have found a superconductor, at ambient pressure at temperatures above 100°C, which they call LK-99. Two of the authors are authors of both articles.  

By comparison, the known room-pressure superconductor of the highest critical temperature (the temperature at which it becomes superconducting) superconducts only below about -135º, although at high pressures some do so at higher temperatures. In a superconductor the resistance to electric current is cancelled out and magnetic fields are expelled. The measurements shown by the authors show that above 100º there is a transition in the system.  

In my opinion, the results are not sufficiently convincing that the state they observe at lower temperatures is superconducting, both because of the lack of measurements of resistivity and magnetic susceptibility over a wider temperature range, and because of the way these quantities, in particular resistivity, depend on temperature. It is necessary to wait for other groups to make more careful studies of this material.   

The theoretical and data analysis in the second article is, in my opinion, particularly bold, discussing a metal-insulator transition without giving the most basic material information, which would be the band structure, guessing at important superconducting information, such as the symmetry of its order parameter, from measurements from which it is difficult to obtain this information, and including statements that are not correct.