Source capture
Authors Aleksandr V. Korolev, Evgeny F. Talantsev
arXiv / Publisher https://arxiv.org/abs/2602.23240
PDF https://arxiv.org/pdf/2602.23240
Relevance score 5.267
Primary category cond-mat.supr-con
Published 2026-02-27
Research paradigm Theoretical
Sample form Single Crystal

Summary

This paper points out that Li et al. made three errors in calculating the superconducting volume fraction from zero-field-cooled (ZFC) and field-cooled (FC) magnetization measurements on single crystals of the high-pressure nickelate superconductor La2SmNi2O7. First, due to the paramagnetic Meissner effect (Wohlleben effect), the magnetic moment in FC mode can be either positive or negative, and thus cannot be used to calculate the superconducting volume fraction. Second, reanalysis of Li et al.'s ZFC data reveals that, according to their own calculation method, the superconducting volume fraction should be 22.8%, not the reported 62.1%—a discrepancy of about a factor of three, primarily arising from differences in the demagnetization factor (Li et al. used 0.849, while the authors calculated 0.81548 using Brandt's formula). Third, even if the ZFC magnetic moment value is correctly calculated, it cannot be directly used to determine the superconducting volume fraction, because there are infinitely many shapes and distributions of superconducting regions smaller than the actual sample size that can produce the same measured magnetic moment. The authors emphasize that they agree with Li et al.'s experimental confirmation of bulk superconductivity in pressurized nickelates, but argue that these calculation errors need to be corrected to avoid misleading future research.

Materials

Methods

Keywords

Highlights

  • Points out three specific errors in the volume fraction calculation by Li et al.
  • Demonstrates that infinitely many smaller superconducting regions can produce the same measured moment.
  • Calls for correction of published values to avoid misleading future research.

Conclusions

  • The reported superconducting volume fraction of 62.1% for La2SmNi2O7 is a threefold overestimation.
  • Correct calculation yields about 22.8%, due to differences in demagnetization factor and formula.
  • FC data cannot be used for volume fraction calculation due to paramagnetic Meissner effect.
  • The approach using ratio of measured to ideal Meissner moment is fundamentally ambiguous for volume fraction determination.

Main claims

  • Li et al. made a threefold error in calculating superconducting volume fraction from ZFC data; correct ZFC fraction is 22.8% not 62.1%
    • Evidence: From abstract: 'Li et al. made a threefold error in their calculations of the superconducting phase fraction in La2SmNi2O7',Calculation yields 22.8% vs reported 62.1%
  • FC data cannot be used for superconducting volume fraction calculations due to paramagnetic Meissner effect (Wohlleben effect)
    • Evidence: From text: 'the FC data cannot be used for any superconducting phase fraction calculations, because of the paramagnetic Meissner effect'

Workflow

Not available in this batch.