Hysteresis loops in measurements of the magnetic moment of hydrides under high pressure: Implications for superconductivity

Abstract

Measurements of magnetic moments of hydride materials under high pressure have been claimed to prove the existence of superconductivity in these materials (Drozdov et al., 2015; Minkov et al., 2021; Minkov et al., 2022; Minkov et al., 2023; Eremets et al., 2022) . However, detection of the signal from the small sample requires subtraction of a large background contribution whose details are largely unknown. Here we analyze reported measurements and point out that the resulting hysteresis loops are incompatible with the conclusion that they result from superconductivity, independent of what assumptions are made about the background signal. We argue that this also invalidates the conclusion that the magnetic moment measured after the external magnetic field is turned off is evidence for trapped magnetic flux resulting from superconducting currents, as proposed in Minkov et al. (2023). Our results imply that to date no magnetic evidence for the existence of high temperature superconductivity in hydrides under pressure exists, despite multiple claims to the contrary.