The First Room-Temperature Ambient-Pressure Superconductor

[volker]

https://arxiv.org/abs/2307.12008
Link to the full paper in the top right corner.

 

[JohnRoberts]

I won't pretend to understand that abstract, but room temperature superconducting could be significant for utility power transmission lines.

JR

 

[Rusan]

I need to lay hold on some of that LK-99. Just think how much audiophools would pay for superconducting interconnect, speaker and power cables!

Rusan

 

[user 37518]

I am not sure what that Tc spec means, but it is rated at 400K, that is 127 °C. I don't think they refer to that as ambient temperature, do they?

 

[sahib]

Quite badly written paper.

I would expect that, with the critical temperature Tc, they would mean the temperature up to which the material maintains the super conducting characteristic.

However, on page 4 they state "...Therefore, we judge that the critical temperature of LK-99 is over 400 K". Over to me means above. Thats almost 128 degrees C.

You have to assume that the graphs on page 3 belongs to their LK99 material as they fail to tell you. However, see the graph (a) on page 3. Voltage across the material versus applied current at various temperatures.

The black trace at 298K which is about 25 degrees C. That's to me is the average ambient temperature. Correct me if I am reading it wrong but there is a non linear resistive region beyond about 240mA , at which point the resistivity breaks down. I would read that point as the critical current before which the material exhibits superconductivity.

At that point the voltage across the material is about 160mV which gives about 0.66 Ohms.

 

[volker]

Quite badly written paper.

I would expect that, with the critical temperature Tc, they would mean the temperature up to which the material maintains the super conducting characteristic.

However, on page 4 they state "...Therefore, we judge that the critical temperature of LK-99 is over 400 K". Over to me means above. Thats almost 128 degrees C.

You have to assume that the graphs on page 3 belongs to their LK99 material as they fail to tell you. However, see the graph (a) on page 3. Voltage across the material versus applied current at various temperatures.

The black trace at 298K which is about 25 degrees C. That's to me is the average ambient temperature. Correct me if I am reading it wrong but there is a non linear resistive region up to about 240mA , at which point the resistivity breaks down. I would read that point as the critical current after which the material exhibits resistivity.

At that point the voltage across the material is about 160mV which gives about 0.66 Ohms.

I saw a very critical response yesterday as well, translated from here, they think it might be bogus or misrepresented data:

I work in the field and we discussed the preprint a bit in the research group this morning. In short, we don't believe a word of it:

Figures 1(a) and (c) are implausible. Usually something like this looks like this. Note the gradual increase at low currents, this effect is to be expected especially with magnetic fields.

Fig. 1(d) cannot be correct either. 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 that 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). It will look like that.

In this case, however, the temperature dependency does not agree at all with the critical currents of Figs. 1(a) and (c).

Also, that ALL the values in Fig. 1(d) are negative is extremely unusual, but that could perhaps be argued with.

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.

I am very familiar with the described experimental setup / the cryostat. There is no reasonable reason why the authors did not measure at higher temperatures to show that the behavior is markedly different above Tc ~ 400K. For example, a temperature dependency of the resistance would have been absolutely necessary.

In general, the paper is very poorly written. The data is under-discussed, the explanations are sparse, and the work cited is, shall we say, sparse. That doesn't exactly inspire confidence in what the authors measured and claim to have seen.

My personal assumption is that the authors measured an insulator, so no current flowed and therefore 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), breakdowns may occur and a current begins to flow. That would explain the sharp increase.

I never got very deep into material science, but it's still interesting to follow what is possibly going on.

 

[sahib]

I have pretty much zero knowledge in material science. I was only looking at it with my electrical engineering eyes.

Not that matters but I have corrected a typo in my last sentence.

 

[living sounds]

I won't pretend to understand that abstract, but room temperature superconducting could be significant for utility power transmission lines.

JR

Maybe, but one of the most important applications would be the holy grail of energy production - the fusion reactor. Superconductivity allows for much more powerful eletromagnets, and these play a vital role in most fusion reactor designs.

Alas, it seems doubtful that a breakthrough has actually been achieved. Scientists around the globe are currently trying to replicate the claims of that pre-publication paper.

 

[JohnRoberts]

Maybe, but one of the most important applications would be the holy grail of energy production - the fusion reactor. Superconductivity allows for much more powerful eletromagnets, and these play a vital role in most fusion reactor designs.

Alas, it seems doubtful that a breakthrough has actually been achieved. Scientists around the globe are currently trying to replicate the claims of that pre-publication paper.

Fusion power would be nice, but lower loss mains power distribution could provide a huge practical benefit. Sadly the huge solar/wind farms are not located in city parks, so the energy needs to get moved to where it is needed.

So far most superconductors require strict temperature management. I could image cascade failures if the temperature lost regulation and the conductors became resistive generating significant heat (bad scifi plot).

JR

 

[living sounds]

Two independent research groups could not replicate the claims.

https://arxiv.org/abs/2307.16402https://arxiv.org/abs/2307.16802

 

[JohnRoberts]

Yup I saw an article in the newspaper suggesting that this same guy was busted for faking results in an earlier study, while they are raising millions of dollars and filing patents. If it sounds too good to be true?

JR

 

[user 37518]

Apparently it was all a sham

 

[JohnRoberts]

A controversial room-temperature superconductor result has been retracted

Easy come, easy go....

JR

 

[5v333]

Critical temperature T_c is the temperature at which the "critical point" is found.
Above T_c a material will never be found in a liquid state for any value in pressure.