arXiv subjects
Publications and source records attributed to J. E. Hirsch.
In Ref. [1], arXiv:2511.03384, Markos and Hlubina argue that "contrary to the expectations of Hirsch" [2] the conventional theory of superconductivity correctly describes the dynamics of the Meissner effect. Here I point out the flaws in their arguments that render them invalid, and propose an experiment to shed further light on these issues.
The Meissner effect, the expulsion of magnetic field from the interior of a metal entering the superconducting state, is arguably the most fundamental property of superconductors, discovered in 1933. The conventional theory of superconductivity developed in 1957 is generally believed to fully explain the Meissner effect. We will review the arguments that support this consensus, rooted in the concept of emergence. However, recent work has shown that there are questions related to momentum conservation in the process of magnetic field expulsion that have not been addressed within the conventional theory. Within a reductionist approach, it has been proposed that those questions can only be resolved by introducing physics that is not part of the conventional theory, namely that there is radial motion of electric charge in the transition process. This is consistent with the behavior of classical plasmas, where motion of magnetic field lines is always associated with motion of charges. We review how this approach explains puzzles associated with momentum transfer between electrons and ions in the Meissner effect. Whether or not radial charge motion is associated with the Meissner effect has fundamental implications regarding superconductivity mechanisms in materials and regarding strategies to search for new materials with higher superconducting transition temperatures. Therefore, adjudication of this question is urgent and important.
In Entropy 24, 83 (2022) [1], titled "The Law of Entropy Increase and the Meissner Effect", A. Nikulov claims that the Meissner effect exhibited by type I superconductors violates the second law of thermodynamics. Contrary to this claim, I show that the Meissner effect is consistent with the second law of thermodynamics provided that a mechanism exists for the supercurrent to start and stop without generation of Joule heat. The theory of hole superconductivity provides such a mechanism, the conventional theory of superconductivity does not. It requires the existence of hole carriers in the normal state of the system.
We consider a type I superconducting body that contains one or more holes in its interior that undergoes a transition between normal and superconducting states in the presence of a magnetic field. We argue that unlike other thermodynamic systems that undergo first order phase transitions the system cannot reach its equilibrium thermodynamic state, and that this sheds new light on the physics of the Meissner effect. How the Meissner effect occurs has not been addressed within the conventional theory of superconductivity, BCS. The situation considered in this paper indicates that expulsion of magnetic field requires physical elements absent from Hamiltonians assumed to describe superconductors within BCS theory. These physical elements are essential components of the alternative theory of hole superconductivity.
In a recent Comment (arXiv:2411.10522, Nat Rev Phys 7, 2 (2025)), fifteen prominent leaders in the field of condensed matter physics declare that hydride superconductivity is real and urge funding agencies to continue to support the field. I question the validity and constructiveness of their argument.
The preceding Comment [1], previously posted as arXiv:2312.04495 [2], on our paper J. Supercond. Nov. Mag. 35, 3141 (2022) [3] provides a welcome opportunity to clarify what we understand to be pervading misconceptions by Eremets, Minkov and coauthors in regard to our analysis [3] of their trapped flux experiments in hydrides under pressure [4]. We hope that this Reply [5] will help readers interested in hydride superconductivity sort out between different claims and counterclaims in the literature and inform their views based on verifiable facts.
In Nat Comm. 13,3194 (2022) [1] and an "Author Correction" to it [2], Minkov et al. presented magnetization data versus applied magnetic field for H_3S and LaH_10 under pressure, argued that the data provide evidence that these materials are superconducting at high temperatures, and extracted from the reported data the behavior of lower critical fields versus temperature. In several papers [3,4,5,6] analyzing Refs. [1,2] it was shown that the published magnetization data could not have been obtained from the reported measured data through the processes described in Refs. [1,2]. Recently, Minkov et al performed a revaluation of their experimental results [7] and argued that the results derived from their new analysis are consistent with the results reported earlier [1]. In addition, they made public the underlying data [8] from which the data published in Ref. [1] were derived. In this paper we analyze those underlying data and conclude that (a) the data published in Ref. [1] are incompatible with the underlying measured data, and (b) the revaluation analysis presented in Ref. [7] does not support the conclusions drawn by the authors in Ref. [7] nor Ref. [1].
I analyze the implications of the recently published "Author Correction" (Nat Commun 14, 5322 (2023)) to a paper by Eremets and coauthors reporting magnetization measurements on hydrides under high pressure (Nat Commun 13, 3194 (2022)) to the understanding of the validity and reproducibility of the published data. This paper is a compilation of several different papers already published or to be published in the scientific literature.
In their paper arXiv:2405.08189, Supercond. Sci. Technol. 37 (2024) 065010 [1], Bud'ko et al. present experimental results for trapped magnetic flux for a tiny sample of a type II superconductor. The paper aims to provide evidence in support of the interpretation that similar measurements performed in samples of hydrogen-rich materials under high pressure by Minkov, Bud'ko and coauthors [2] are conclusive evidence [3] for superconductivity in hydrides under pressure. Here we point out that the new evidence presented by Bud'ko et al. [1] further supports our interpretation [4],[5] that the reported measurements of trapped flux on hydrides under pressure [2] are evidence that the samples are $not$ superconducting.
In Ref. [1] we surveyed the known hydride superconductors, and compared their resistive behavior to that of typical known superconductors, including conventional (e.g. NbN and MgB$_2$) and unconventional (e.g. YBCO) superconductors, and concluded that the behavior of the hydrides was indicative of nonstandard or no superconductivity. In the preceding comment, Talantsev, Minkov, Balakirev and Eremets [2] (arXiv:2311.07865) claim that we presented a "flawed analysis and a selective and inaccurate report of published data." Here we show that this claim is wrong.
It is generally believed that sulfur hydride under high pressure is a high temperature superconductor. In National Science Review 6, 713 (2019) Huang and coworkers reported detection of superconductivity in sulfur hydride through a highly sensitive ac magnetic susceptibility technique and an unambiguous determination of the superconducting phase diagram. In this paper we present evidence showing that the experimental results reported in that paper do not support the conclusion that sulfur hydride is a superconductor.
In the recently posted arXiv:2312.04495v3 [1], its authors used a computer code written by me supplied to them by the authors of Ref. [2], and claimed that the results that they obtained invalidate the results and conclusions presented in the paper J. Supercond. Nov. Mag. 35, 3141-3145 (2022) by F. Marsiglio and myself [2]. Here I point out that the authors' claim (i) resulted from improper unauthorized use of my computer code, (ii) is wrong, and (iii) is misleading to the scientific community.
In Nat Commun 13, 3194 (2022) [1], Minkov et al. reported magnetization measurements on hydrides under pressure that claimed to find a diamagnetic signal below a critical temperature demonstrating the existence of superconductivity. Here we present an analysis of raw data recently released [2] by the authors of [1] that shows that the measured data do not support their claim that the samples exhibit a diamagnetic response indicative of superconductivity. We also point out that Ref. [1] in its original form omitted essential information that resulted in presentation of a distorted picture of reality, and that important information on transformations performed on measured data remains undisclosed. Our analysis also calls into question the conclusions of Minkov et al's trapped flux experiments reported in Nat. Phys. (2023) [3] as supporting superconductivity in these materials. This work together with earlier work implies that there is no magnetic evidence for the existence of high-temperature superconductivity in hydrides under pressure.
In Ref. [1], Minkov et al. reported measurements of the magnetic moment that remains after a magnetic field is turned on and then turned off for hydride materials under high pressure in a diamond anvil cell. In Refs. [2,3], Minkov et al. reported magnetization measurements on the same samples as a function of applied magnetic field. Here we argue that the latter indicate that the signal measured in the former does not provide evidence for superconductivity in these samples. Instead, the measured signal likely originates in ferromagnetism of either the sample or the background.
The resistive transition width of a recently discovered room temperature near-ambient-pressure superconductor [1] changes by more than three orders of magnitude between different samples, with the transition temperature nearly unchanged. For the narrowest transitions, the transition width relative to $T_c$ is only $0.014 \%$. The voltage-current characteristics indicate vanishing critical current, and the normal state resistance is unusually small. These anomalous behaviors and other issues indicate that this system is not a superconductor. Implications for other hydrides are discussed.
It has recently been reported that hydrogen-rich materials under high pressure trap magnetic flux, a tell-tale signature of superconductivity [arXiv:2206.14108v1]. Here we point out that under the protocol used in these experiments the measured results indicate that the materials don't trap magnetic flux. Instead, the measured results are either experimental artifacts or originate in magnetic properties of the sample or its environment unrelated to superconductivity, Together with other experimental evidence analyzed earlier, this clearly indicates that these materials are not superconductors. {\bf In a second part, we discuss magnetic field screening and expulsion.}
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 lanthanum hydride under high pressure [1], and more recently Eremets et al. argued that "the arguments against superconductivity (in hydrides) can be either refuted or explained" [2]. Instead, we show here that the evidence presented in those papers does not support the case for superconductivity in these materials. Together with experimental evidence discussed in earlier papers, we argue that this strongly suggests that hydrides under pressure are not high-temperature superconductors.
In Phys. Rev. Lett. 102, 197002 (2009) it was reported that the element Eu becomes superconducting in the pressure and temperature range [84-142GPa], [1.8-2.75K]. The claim was largely based on ac susceptibility measurements. Recently reported ac susceptibility measurements on a hydride compound under pressure that appears to become superconducting near room temperature (Nature 586, 373 (2020)) cast serious doubt on the validity of the results for Eu as well as for the hydride. Here I present results that shed new light on the true behaviour of Eu. It is argued that the experiments on Eu have to be repeated to either validate or rule out the claim that it is a superconducting element.