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Observation of zero resistance above 100 K in Pb₁₀₋ₓCuₓ(PO₄)₆O

arxiv.org

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Re: Observation of zero resistance above 100 K in Pb₁₀₋ₓCuₓ(PO₄)₆O

#21

Post by segfaultbuserr »

lifthrasiir wrote: post #8

I'm very much conservative about this paper because while the graph in Fig. 3a says $T_c^{zero}$ being 110 K, the "zero" resistance is actually only 1e-5 Ω (!) and even if the sample is possibly superconducting its critical temperature would be much lower than 110 K anyway. I'm aware of the difficulty in obtaining larger samples, but the label in that graph is really misleading regardless.

The resistance curve stopped at 1e-5 Ω because it has nearly reached the resolution limit of their instrument. Using 4-wire Kelvin sensing, the measurement current was 1 mA, the voltage read-out across the material was around 1 to 10 nanovolts - this is around the scale that some of the world's best general-purpose voltmeters can measure down to. The authors assumed that the negligible voltage drop, combined with the abrupt drop and flattening of the resistance vs temperature curve is already a convincing-enough indication of superconductivity.

Hopefully more rigorous testing will be done by one of the teams later.

Re: Observation of zero resistance above 100 K in Pb₁₀₋ₓCuₓ(PO₄)₆O

#22

Post by ant6n »

jesprenj wrote: post #5

Is this one also written in Word so it automatically loses LaTeX-credibility, as was commented under the first paper? (:

Maybe some people wanna focus on the work and not on the geek cred.

(I need to write some thesis like thing soon, like 15 years after my masters thesis that was written in latex, and do I really want to bother setting latex up again and futz with templates and fight for correctly positioned figures, or just use Word and be done with it?)

Re: Observation of zero resistance above 100 K in Pb₁₀₋ₓCuₓ(PO₄)₆O

#23

Post by segfaultbuserr »

nukros wrote: post #16
lifthrasiir wrote: post #8

I'm very much conservative about this paper because while the graph in Fig. 3a says $T_c^{zero}$ being 110 K, the "zero" resistance is actually only 1e-5 Ω (!) and even if the sample is possibly superconducting its critical temperature would be much lower than 110 K anyway. I'm aware of the difficulty in obtaining larger samples, but the label in that graph is really misleading regardless.

The random jumps in the resistivity around 250 K suggests that there is very bad contact resistance or a possible alternate current path. The drop in resistance doesn’t look like a typical phase transition (it is very broad in temperature). My guess would be that the voltage leads are not very well connected to the region of the sample that the current is flowing through. This could actually give a drop in the measur…

One of the authors commented in their previous video pre-announcement that they suspect it was a probe cleanliness problem, which they would investigate later.

Re: Observation of zero resistance above 100 K in Pb₁₀₋ₓCuₓ(PO₄)₆O

#25

Post by lifthrasiir »

segfaultbuserr wrote: post #21
lifthrasiir wrote: post #8

I'm very much conservative about this paper because while the graph in Fig. 3a says $T_c^{zero}$ being 110 K, the "zero" resistance is actually only 1e-5 Ω (!) and even if the sample is possibly superconducting its critical temperature would be much lower than 110 K anyway. I'm aware of the difficulty in obtaining larger samples, but the label in that graph is really misleading regardless.

The resistance curve stopped at 1e-5 Ω because it has nearly reached the resolution limit of their instrument. Using 4-wire Kelvin sensing, the measurement current was 1 mA, the voltage read-out across the material was around 1 to 10 nanovolts - this is around the scale that some of the world's best general-purpose voltmeters can measure down to. The authors assumed that the negligible voltage drop, combined with the…

Which is indeed their argument. But in that case they haven't proved that $T_c^{zero}$ = 110 K, they only proved that $T_c^{zero}$ < 110 K. (And I should also note that $T_c^{zero}$ doesn't imply the actual critical temperature $T_c$, while the title strongly suggests so.)

Re: Observation of zero resistance above 100 K in Pb₁₀₋ₓCuₓ(PO₄)₆O

#26

Post by keyle »

> In conclusion, we successfully synthesized the compound Pb10-xCux(PO4)6O, and observed the zero resistance above 100 K. However, the Meissner effect has not been observed yet in our samples, which suggests that the superconducting volume is relatively low.

In conclusion, ... nothing?

Re: Observation of zero resistance above 100 K in Pb₁₀₋ₓCuₓ(PO₄)₆O

#27

Post by [deleted] »

kvandy wrote: post #12
wsieroci wrote: post #7

Could someone explain why this is important? What is the consequence of the existence of Superconductors like that?

My understanding is that this unlocks future-tech... Post quantum computing, hyper efficient rail tech, fast charging batteries, etc. Pretty neat stuff, and even cooler to be able to follow this as it develops.

[deleted]

Re: Observation of zero resistance above 100 K in Pb₁₀₋ₓCuₓ(PO₄)₆O

#28

Post by userbinator »

I completely ignored the authors (as I usually do) and started reading it, noticed the slightly odd phrasing, and then chuckled at "mad great efforts" and then "a very excited news" a short while later before looking at the authors and realising the country of origin.

Re: Observation of zero resistance above 100 K in Pb₁₀₋ₓCuₓ(PO₄)₆O

#29

Post by n2d4 »

wsieroci wrote: post #7

Could someone explain why this is important? What is the consequence of the existence of Superconductors like that?

In the most ELI5 way possible, a superconductor is a material that doesn't lose any energy or produce heat when used as a cable/wire, and at the same time also a very strong magnet.

MRIs and powerlines are more obvious applications, but theoretically you can do a lot of cool stuff (batteries with zero energy loss, heat-efficient computers, etc [1]). If true, LK-99 would allow these things to happen at room temperature instead of negative whatever degrees, making them much more useful.

[1] https://en.m.wikipedia.org/wiki/Technological_applications_o...

Re: Observation of zero resistance above 100 K in Pb₁₀₋ₓCuₓ(PO₄)₆O

#30

Post by tomohelix »

Summary of events so far:

The claim: Room temp (~300K) superconductor exists and we got it!

The replication attempts: The production method is so poorly documented only a fraction of the samples being made shows any interesting properties. And among those interesting ones, results varies. Very few, if any, attempt actually completely shows the entire spectrum of properties and behaviors of a true superconductor at room temperature yet. But those kinds of experiments take time so it isn't an indicator of problem.

My take: It is probably something interesting but not well understood. Best case scenario, the original sample in the Korean lab probably won the synthesis lottery and is actually a true room temp superconductor. Worst case scenario, we got another class of high temp (warmer than liquid nitrogen but cold enough that applications are limited) superconductor but nothing revolutionary since at this point, it is pretty conclusive that there is something interesting with LK-99.

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