3 ms·

> Has there been any commentary on that? German, but nevertheless: http://blog.fefe.de/?ts=9a3f8740 http://blog.fefe.de/?ts=9a3f8740 "I work in the field [...

> Has there been any commentary on that? German, but nevertheless: http://blog.fefe.de/?ts=9a3f8740 http://blog.fefe.de/?ts=9a3f8740 "I work in the field [...] we don't believe a word of this. [...] The data set in Fig. 4(b) is also a treat. It is VERY unusual when the heat capacity decreases again at high temperatures. This can happen at low temperatures, but not at high temperatures. [...] My personal assumption is that the authors measured an insulator, so no current flow and therefore no voltage occurred (4-point measurement). This would look like a superconductor. But if you then turn up the current (i.e. the applied voltage), breakdowns may occur and a current begins to flow. That would explain the sharp increase."

scarmig 3y ago
Nice find.
- distortionfield 3y ago
  Not really, it’s just more speculation about the experiment. It’s worth as much as anyone else’s salt about the matter.
  - fh973 3y ago
    It's from a guy of the Max Planck Institute for Solid State Research.
    - nemo44x 3y ago
      He sounds rather bitter and arrogant. He basically just called them idiots. As if none of the researchers would have noticed the measurement error. Perhaps he’s right - we’ll know in a few days I assume. I do hope they are right though not only because it would be a huge leap but also because I’d love to see this guys reaction.
      - stu255 3y ago
        Lee and Kim have been working on this stuff for a long time. They published prematurely after major falling out within their institute. This isn't 1 experiment as the Germans seem to think. There are multiple papers, patents, etc. The main focus of these papers has been to make huge claims and make replication very easy. They are "all in" and they want others to call. If they were bluffing they would be heavy on results and light/secretive on how to make the stuff (trade secret, etc). That's why there are 2x papers published within 3 hours, both with different authors, and you have one author telling New Scientist he did not approve of a paper naming him as an author.
      - xdennis 3y ago
        > He sounds rather bitter and arrogant. That might be your interpretation of it. I think the Germans would call it being straightforward.
        groestl 3y ago
        It's a cultural thing, we tend to spare the buns from the sandwich feedback ;)
RyanAdamas 3y ago
Wow, that's pretty damning. Good one.
- jeepers6 3y ago
  “Damning” is the wrong word here. “Damning” would be “oh, look, the researchers forgot that the plot showing zero voltage also shows current dropping to zero. They’re clearly measuring a bad contact.” But the papers don’t show that. There’s no obvious contradiction unless you make some big assumptions.
  - singularity2001 3y ago
    OP works in the field and provides good arguments. You can translate the full blog post.
amluto 3y ago
A 4-point measurement of an insulator would show zero current, as far as I know. A more plausible idea IMO is that it could be a 4-point measurement of a highly inhomogeneous sample. If the current probes make contact with conductive parts of the sample, and there is a conductive path between them, but one or both voltage probes are not contacting the conductive path, then the voltage measurement would be garbage and potentially zero. I don’t think this is much of a problem when measuring conventional conductors (you don’t need a particularly good contact, which is much of the point), but a lot of superconductors are oddball materials where, under conditions where they fail to superconduct, they barely conduct at all. So maybe the sample has a conducting phase and an insulating phase?
- BizarroLand 3y ago
  Wouldn't it be odd for an amalgam of lead and copper to be non-conductive? I know they were formed from sulfur compounds, but the production process should have eliminated those compounds, and the final forming is done in a vacuum so there shouldn't be any oxide generation to form non-conductive barriers. I don't know much about the process but shouldn't they be testing resistance in a superconductor?
  - scentoni 3y ago
    It’s not an amalgam (that means a mercury alloy) or any metallic alloy. It’s an oxide (more complicated than that but there’s more oxygen atoms than metal atoms).
    - BizarroLand 3y ago
      Amalgam can also mean, "A mixture or combination of different things" such as "an amalgam of musical genres" or "an amalgam of unsavory dog food flavors", which, since we aren't talking about mercury at all, nor are we talking about any form of dentistry, should have be evident and deducible from the context. https://www.oxfordlearnersdictionaries.com/definition/english/amalgam https://www.oxfordlearnersdictionaries.com/definition/englis... And we very much are talking about an alloy, which is a "metallic substance composed of two or more elements" https://www.britannica.com/technology/alloy https://www.britannica.com/technology/alloy Lead is a metal. Copper is a metal, a combination of 2 metals is an alloy. However, you are right, I did overlook that the compound is an oxide, my bad.
deleted 3y ago
[deleted]
top_sigrid 3y ago
Came here to mention this. Here is a full deepl translation of the post, for those who are interested (in the above linked post of a blog the blog author recites a mail from one of his readers): "I work in the field and we discussed the preprint a bit in the research group this morning. In a nutshell, we don't believe a word of it: Fig. 1(a) and (c) are implausible. Normally, this sort of thing looks like this. Note the gradual increase at low currents, this effect is especially expected for magnetic fields. Also Fig. 1(d) cannot be correct. At Tc ~ 400K the Meissner effect would displace a much stronger field than 10 Oe = 1 mT. I.e. the distinction between FC (field cooled) and ZFC (zero-field cooled) should not be so pronounced. It should look more like this. What the authors might mean is that they are outside the Meissner range, which can occur at higher magnetic fields (keyword: Type II superconductors). This then looks like this. But in this case the temperature dependence does not agree at all with the critical currents of Fig. 1(a) and (c). And also that ALL values in Fig. 1(d) are negative is extremely unusual, but this could perhaps be argued. The data set in Fig. 4(b) is also a treat. It is VERY unusual to see the heat capacity decrease again at high temperatures. This can happen at low temperatures, but rather not at high temperatures. I know the described experimental setup / cryostat very well. There is no reasonable reason why the authors did not measure at higher temperatures to show that the behavior above Tc ~ 400K is significantly different. E.g. a temperature dependence of the resistance would have been mandatory. In general, the paper is very poorly written. The data are not adequately discussed, the explanations are poor, and the papers cited are rather, shall we say, meager. This does not inspire confidence in what the authors have measured and want to have seen there. My personal guess is that the authors measured an insulator, accordingly no current flowed, and thus no voltage occurred (4-point measurement). Then it looks like a superconductor. But if you then turn up the current (i.e. the applied voltage), there may be breakdowns and a current starts to flow. This would explain the sudden increase."

scarmig 3y ago

Nice find.

distortionfield 3y ago
Not really, it’s just more speculation about the experiment. It’s worth as much as anyone else’s salt about the matter.
- fh973 3y ago
  It's from a guy of the Max Planck Institute for Solid State Research.
  - nemo44x 3y ago
    He sounds rather bitter and arrogant. He basically just called them idiots. As if none of the researchers would have noticed the measurement error. Perhaps he’s right - we’ll know in a few days I assume. I do hope they are right though not only because it would be a huge leap but also because I’d love to see this guys reaction.
    - stu255 3y ago
      Lee and Kim have been working on this stuff for a long time. They published prematurely after major falling out within their institute. This isn't 1 experiment as the Germans seem to think. There are multiple papers, patents, etc. The main focus of these papers has been to make huge claims and make replication very easy. They are "all in" and they want others to call. If they were bluffing they would be heavy on results and light/secretive on how to make the stuff (trade secret, etc). That's why there are 2x papers published within 3 hours, both with different authors, and you have one author telling New Scientist he did not approve of a paper naming him as an author.
    - xdennis 3y ago
      > He sounds rather bitter and arrogant. That might be your interpretation of it. I think the Germans would call it being straightforward.
      - groestl 3y ago
        It's a cultural thing, we tend to spare the buns from the sandwich feedback ;)

RyanAdamas 3y ago

Wow, that's pretty damning. Good one.

jeepers6 3y ago
“Damning” is the wrong word here. “Damning” would be “oh, look, the researchers forgot that the plot showing zero voltage also shows current dropping to zero. They’re clearly measuring a bad contact.” But the papers don’t show that. There’s no obvious contradiction unless you make some big assumptions.
- singularity2001 3y ago
  OP works in the field and provides good arguments. You can translate the full blog post.

amluto 3y ago

A 4-point measurement of an insulator would show zero current, as far as I know. A more plausible idea IMO is that it could be a 4-point measurement of a highly inhomogeneous sample. If the current probes make contact with conductive parts of the sample, and there is a conductive path between them, but one or both voltage probes are not contacting the conductive path, then the voltage measurement would be garbage and potentially zero. I don’t think this is much of a problem when measuring conventional conductors (you don’t need a particularly good contact, which is much of the point), but a lot of superconductors are oddball materials where, under conditions where they fail to superconduct, they barely conduct at all. So maybe the sample has a conducting phase and an insulating phase?

BizarroLand 3y ago
Wouldn't it be odd for an amalgam of lead and copper to be non-conductive? I know they were formed from sulfur compounds, but the production process should have eliminated those compounds, and the final forming is done in a vacuum so there shouldn't be any oxide generation to form non-conductive barriers. I don't know much about the process but shouldn't they be testing resistance in a superconductor?
- scentoni 3y ago
  It’s not an amalgam (that means a mercury alloy) or any metallic alloy. It’s an oxide (more complicated than that but there’s more oxygen atoms than metal atoms).
  - BizarroLand 3y ago
    Amalgam can also mean, "A mixture or combination of different things" such as "an amalgam of musical genres" or "an amalgam of unsavory dog food flavors", which, since we aren't talking about mercury at all, nor are we talking about any form of dentistry, should have be evident and deducible from the context. https://www.oxfordlearnersdictionaries.com/definition/english/amalgam https://www.oxfordlearnersdictionaries.com/definition/englis... And we very much are talking about an alloy, which is a "metallic substance composed of two or more elements" https://www.britannica.com/technology/alloy https://www.britannica.com/technology/alloy Lead is a metal. Copper is a metal, a combination of 2 metals is an alloy. However, you are right, I did overlook that the compound is an oxide, my bad.

deleted 3y ago

[deleted]

top_sigrid 3y ago

Came here to mention this. Here is a full deepl translation of the post, for those who are interested (in the above linked post of a blog the blog author recites a mail from one of his readers): "I work in the field and we discussed the preprint a bit in the research group this morning. In a nutshell, we don't believe a word of it: Fig. 1(a) and (c) are implausible. Normally, this sort of thing looks like this. Note the gradual increase at low currents, this effect is especially expected for magnetic fields. Also Fig. 1(d) cannot be correct. At Tc ~ 400K the Meissner effect would displace a much stronger field than 10 Oe = 1 mT. I.e. the distinction between FC (field cooled) and ZFC (zero-field cooled) should not be so pronounced. It should look more like this. What the authors might mean is that they are outside the Meissner range, which can occur at higher magnetic fields (keyword: Type II superconductors). This then looks like this. But in this case the temperature dependence does not agree at all with the critical currents of Fig. 1(a) and (c). And also that ALL values in Fig. 1(d) are negative is extremely unusual, but this could perhaps be argued. The data set in Fig. 4(b) is also a treat. It is VERY unusual to see the heat capacity decrease again at high temperatures. This can happen at low temperatures, but rather not at high temperatures. I know the described experimental setup / cryostat very well. There is no reasonable reason why the authors did not measure at higher temperatures to show that the behavior above Tc ~ 400K is significantly different. E.g. a temperature dependence of the resistance would have been mandatory. In general, the paper is very poorly written. The data are not adequately discussed, the explanations are poor, and the papers cited are rather, shall we say, meager. This does not inspire confidence in what the authors have measured and want to have seen there. My personal guess is that the authors measured an insulator, accordingly no current flowed, and thus no voltage occurred (4-point measurement). Then it looks like a superconductor. But if you then turn up the current (i.e. the applied voltage), there may be breakdowns and a current starts to flow. This would explain the sudden increase."