Clear evidence against superconductivity in hydrides under high pressure

Abstract

The Meissner effect, magnetic field expulsion, is a hallmark of superconductivity. Associated with it, superconductors exclude applied magnetic fields. Recently Minkov et al. presented experimental results reportedly showing “definitive evidence of the Meissner effect” in sulfur hydride and lan-thanum hydride under high pressure1. Instead, we show here that the evidence presented in that paper does not support the case for superconductivity in these materials. Together with experimental evidence discussed in earlier papers, we argue that this clearly indicates that hydrides under pressure are not high temperature superconductors.

Nonstandard superconductivity or no superconductivity in hydrides under high pressure

“…Since we wrote Ref. [1], substantial additional evidence has emerged that the hydrides are either "nonstandard superconductors" or, more likely, not superconductors [18][19][20]. In addition, we point out that two papers [21,22] claiming high temperature superconductivity in hydrides that showed anomalous behavior in the resistance data [14,16] have been retracted [23,24] and a third one [25] is under investigation, and other claims [26][27][28] have not been reproduced.…”

Are hydrides under high pressure high temperature superconductors?

“…Fig. 1a shows also that the magnetic moment under zero field cooling (ZFC) reported in 2022 [3] was approximately three times smaller than that reported in 2015 [1], for samples that were similar in diameter and thickness as estimated in the papers [1,2]. Unlike under the FC protocol, under ZFC the measured signal is expected to depend only on sample volume and not on sample quality, casting doubt on the validity of these results.…”

“…The field is entirely driven by theory, and as a consequence is subject to confirmation bias. When a sample predicted to be superconducting is found to show a drop in resistance, this is immediately interpreted as indicating superconductivity, ignoring the fact that there are other reasons why heterogeneous very small samples under enormous pressures could exhibit such drops [2]. Magnetic evidence that these materials are superconductors remains scarce, spotty, contradictory and irreproducible.…”