arXiv subjects

Aleksandr V. Korolev

Publications and source records attributed to Aleksandr V. Korolev.

3 recordsLinked to original sources

arXiv2026

On the estimating the superconducting volume fraction from the internal magnetic susceptibility

Zhang et al.$^1$ reported zero-field cooled (ZFC) and field cooled (FC) data measured in a highly compressed $Pr_4Ni_3O_{10}$ single crystal. These measurements provide unambiguous confirmation of bulk superconductivity in pressurized Ruddlesden-Popper nickelates. Zhang et al.$^1$ applied an equation (described in Refs.$^{2,3}$) to recalculate ZFC data measured in a $Pr_4Ni_3O_{10}$ (sample S3) in volume fraction $f$ of the superconducting phase in the sample. In result$^1$, $f = 0.85$ was reported for sample S3 at pressure P = 40.2 GPa. The key postulate of the methodology for the calculation of $f$ (see also works$^{4-6}$) is that $f$ is equal to the amplitude of the internal magnetic susceptibility $\vert χ_{internal} \vert $, or $ f = \vert χ_{internal} \vert $. Here we argue that this postulate is incorrect and present counterexample where the $Pr_4Ni_3O_{10}$ sample S3 can exhibit $f < 0.10$ and $\vert χ_{internal} \vert = 0.82 $. In the result, we addressed recent Replies$^{2,3}$ on our Comments$^{7,8}$. Considering that the postulate $ f = \vert χ_{internal} \vert $ is widely used in superconductivity, we extend our request to reconsider the validity of this postulate in the entire field of superconductivity.

cond-mat.supr-con↗

arXiv2026

Threefold error in the reported zero-field cooled magnetic moment of single crystal $La_2SmNi_2O_7$

For a relatively long time, the observation of the DC diamagnetic state in highly compressed nickelate superconductors [1],[2] has been a challenging experimental problem. And recently Li et al.[3] reported on the measurements of the DC diamagnetism in zero-field-cooled (ZFC) and field-cooled (FC) pressurized single crystal $La_2SmNi_2O_7$. From the analysis of experimental data, Li et al.[3] reported that the superconducting phase fraction in their $La_2SmNi_2O_7$ sample measured in the ZFC mode is 62.1%, and the superconducting phase fraction in the FC mode is 14.4%. It should be clarified that we regard the measurements of the DC diamagnetic state [3] in $La_2SmNi_2O_7$ (and more recently in $Pr_4Ni_3O_{10}$ [4]) as outstanding experimental results confirming bulk superconductivity in pressurized nickelates. However, we should note that Li et al.[3] made a threefold error in their calculations of the superconducting phase fraction in $La_2SmNi_2O_7$. We believe that correcting this and other errors in Ref.[3] will benefit the physics community.

cond-mat.supr-con↗

arXiv2026

Nearly twofold overestimation of the superconducting volume fraction in pressurized Ruddlesden-Popper nickelates

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 fraction$f$) reaches 81-86%. We regard outstanding experimental results$^1$; however, our calculations based on the reported experimental datasets$^1$ 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 calculate$f$. To our knowledge, the procedure$^1$ and equation$^1$ for calculating $f$ have never been mentioned or described before, including in Ref.$^1$. Here we argue that the proposed equation$^1$ and procedure$^1$ are incorrect, and that this equation$^1$ 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 date$^{1-4}$. Therefore, we describe the error we discovered in this paper.

cond-mat.supr-con↗