Nearly twofold overestimation of the superconducting volume fraction in pressurized Ruddlesden-Popper nickelates
Abstract
The detection of the DC diamagnetic state in pressurized Ruddlesden-Popper nickelates remained an unsolved experimental problem until recent experiments in which Zhu et al.1 measured the DC diamagnetic responses in zero-field cooled (ZFC) mode in pressurized La4Ni3O10. Zhu et al.1 reported that the ratio of the measured ZFC magnetic moment to the Meissner magnetic moment of the sample (and this ratio was termed the superconducting volume fractionf) reaches 81-86%. We regard outstanding experimental results1; however, our calculations based on the reported experimental datasets1 using the standard procedure showed the ratio to be 51-59%. Upon our request, Zhu et al.1 provided detailed explanations and the equation they used to calculatef. To our knowledge, the procedure1 and equation1 for calculating f have never been mentioned or described before, including in Ref.1. Here we argue that the proposed equation1 and procedure1 are incorrect, and that this equation1 results in multiple overestimations of the superconducting volume fraction in the sample. This overestimation error affects all superconducting volume fractions f in Ruddlesden-Popper nickelates reported to date1-4. Therefore, we describe the error we discovered in this paper.
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