Some remarks on possible superconductivity of composition Pb9CuP6O25 | Hacker News Reader

Some remarks on possible superconductivity of composition Pb9CuP6O25

arxiv.org

179 pointsrsfern92 comments

I think the important part is that AFAIK the superconductivity only happens within the crystalline structure.

If that's the case then we are looking at really limited application. The magic of superconductivity pretty much vanishes the moment it has to interface with any non-superconducting medium. If you want to create lets say a superconducting winding for a magnet, the point of superconductivity is you can push a huge current through the winding with no heating. But nanocrystals can't accomplish it because there will inevitably be spaces between crystals and these spaces will have resistance and will generate heat.

Now, this does not mean there won't be some applications. Nanocrystals or not, they still can be used to levitate trains if we can perfect production of this exotic material.

And, the most important, we may learn more about superconductivity that will allow us to find other superconductors that do not have this limitation.

The entire modern era depends on large single crystals, especially, but not limited to, silicon.

For non-silicon applications, take a glance at some of Cree's products, for example.

High performance gas turbine blades (e.g. in the F-22 engine and apparently some electricity turbines) are single crystal now as well. It's definitely a huge challenge to do manufacture, but possible.

> And, the most important, we may learn more about superconductivity that will allow us to find other superconductors that do not have this limitation.

completely agreed. getting this thing confirmed beyond doubt is not the end, it's a very promising beginning. dump a few billion dollars on it to develop theory, experiment in related substances, maybe there can be something made that's elastic? or maybe this thing can be grown in zero gravity, which (perhaps regrettably) makes Musk the Levi Strauss of the space fabrication era? etc.

There's some very interesting technology for making turbine blades that are effectively single-crystal objects that might just come into play, if that's the case.

Cool study - they made a Pb thin film and compared its superconducting properties to the recent reports on LK-99 reproduction attempts

They’re hypothesizing that people may be getting superconducting nanocrystals embedded in maybe amorphous material. I don’t know if it’s typical to do microscopy in superconductivity research, but it would be super interesting to see more microscopic detail on what people are getting

Electron microscopy might not work. The moving electrons in the SEM or STEM would create a magnetic field that is opposed by the material, and the opposing magnetic field would affect the electrons and probably destroy any possibility of imaging.

Heat the sample to 200C?

That might work. I actually thought of it, but didn't mention it.

What about AFM?

I don't know know if the superconductor has enough phase difference to be picked up in tapping, but who knows

Has anyone produced magnetic cantilevers?

Yes, quite a few companies sell them.

https://en.m.wikipedia.org/wiki/Magnetic_force_microscope

I get the idea of superconducting islands in a non-conducting matrix. What I don't understand is what thin lead films have to do with it, particularly if the superconducting island thing is well established already. What does the lead film experiment add?

> superconducting islands in a non-conducting matrix.

Can somebody who read the article and is knowledgeable in the subject please re-assure me this doesn't mean the material only forms minute super-conducting islands and that we can make wires out of this material in the future?

The material is very fragile, so even if it will be proven to be a superconductor wires are not a possible application.

Nevertheless, there are many applications where it could be used as layers deposited on a rigid substrate, so something like a PCB (a small one, which does not bend) or an interconnection layer for semiconductor chips or superconducting devices like Josephson junctions may be possible.

it’s just a hypothesis, but they are saying that maybe the LK-99 samples people are making look like their figure 4 with tiny superconducting islands of lead

That doesn’t mean we won’t be able to make wires and devices in the future. If it’s confirmed that we’re seeing real superconductivity (especially above room temperature) it’s going to drive a ton of research on finding actually good synthesis recipes to make continuous macroscopic chunks of the stuff, even if the current recipe isn’t particularly optimal

Lead has been used just because it is the cheapest superconductor and it is easily available everywhere.

They have deposited very thin layers of lead on an insulating substrate, making the layers so thin that they became discontinuous.

On such discontinuous layers they have measured a few properties and the resulting curves looked weird, somewhat similar to what has been measured on LK-99.

This was published as a reply to the people who wonder why the measurements done on samples of LK-99 do not resemble those measured on bulk superconductors.

The lead films are a model system that show some parallels to the behavior people have been observing with LK-99. Their point is that if this hypothesis is correct, it should be possible to grow fully dense LK-99 material that has much more robust superconductive properties, and that the difficulty of this synthesis could explain why people are getting conflicting results in their reproduction attempts.

Can someone with more knowledge talk a bit about the most immediate and practical uses of a room temperature semi conductor? From what I understand, non-chemical batteries (ie: current-trapped-forever-in-a-rock), hand held MRI machines, passively levitating trains, and dramatically simpler nuclear reactors are on the table. However, the articles I can grok don’t exactly give a hint as to how far A is from B - ie: does a room temp super conductor solve for 5% or 95% of these challenges?

I’ve never been filled with regret for not going to college. I did extremely well for myself and my family by avoiding it, despite my desire and my love for learning. But reading this… I’m very jealous of you physicists!

Of that particular list, I would say levitating trains are currently solved from a technical view point[0], and are awaiting economic viability.

I know enough about fusion to say while having stronger magnetic fields make things easier, there's a lot of plasma physics that needs to be understood to do confinement. Furthermore the easy reactions all have neutron radiation to deal with so it is an open question if it will avoid all the same social problems fission has had piled on it.

Hand held MRIs... that's a stretch, you can make better detectors with SCs, but even so, I suspect you'll want to wrap the area of interest in some apparatus.

One you didn't mention and I had been somewhat dismissing until last week was energy storage, we have big existing ones already[1] and several of their drawbacks go away if their refrigeration demands drop to 0.

[0]https://www.youtube.com/watch?v=4ZX9T0kWb4Y [1]

>Of that particular list, I would say levitating trains are currently solved from a technical view point[0], and are awaiting economic viability.

No, they're not. They're already economically viable: that's why Japan is building one between Tokyo and Nagoya right now, and it'll be in service later this decade. The current bullet trains are huge money-makers and have been for a long time; the Chuo shinkansen will be too.

China's Maglev keeps losing money.

Something is built and in service == economically viable in decision-makers(often politicians!)' minds != economically viable.

China's "maglev" is a short train to the airport. It's for demonstration purposes only.

Japan's maglev is connecting the largest city in the world with one of its other largest cities. When complete, it'll connect the 3 largest metro areas in the country together. Japan already has a bullet train that does exactly this, and it makes tons of money, and it's been doing so since the 1960s.

Japan's commercial maglev is not yet completed. All current Japanese high speed services are conventional rail. There is a small test track for maglev and an under-construction commercial maglev with no public completion date (https://en.wikipedia.org/wiki/Ch%C5%AB%C5%8D_Shinkansen).

>with no public completion date

Wrong, the first leg will be complete in 2027. It takes some time because 90% of it is underground.

Yes, it's not completed yet, but it doesn't matter: it's virtually guaranteed to be profitable, just because the current shinkansen are.

Japan doesn't subsidize their maglev trains at all?

The point being, RTSC just tears the floor out on some of the operating costs for it, so since all the control schemes and even a lot of the design work is already established practice, maglev /ought/ to proliferate a lot more quickly than, say, municipal scale fusion reactors.

Circular particle accelerators like the LHC, fusion reactors and quantum computers all obtain a large part of their complexity and expense from the cryogenic refrigerators that are necessary for them to work. It goes unnoticed because people think of it as a "solved problem," but keeping tons of material at liquid nitrogen temperatures takes a lot of energy and huge apparatuses.

That's not to mention delays in work too. Every time there's a "quenching" event at the LHC, that's days/weeks/months fixing everything and getting it back down to temp.

I seem to recall they had to shut down for a year or so for upgrades at one point too. Having to work around the cooling had to have affected that timeline.

> material at liquid nitrogen temperatures Even worse sometimes. For the LHC it's liquid helium temperatures!

As I understand it (not an expert) superconducting qubits are strongly impacted by temperature. So they're typically operated at sub-Kelvin temperatures, using liquid helium. Worse yet, they need unobtanium: helium 3.

https://en.m.wikipedia.org/wiki/Dilution_refrigerator

https://threadreaderapp.com/thread/1685088625187495936.html

The most immediate and interesting are improvements to generators (35%) and SQUIDS.

Superconductor though.

A semiconductor is a material that is somewhere in between conductor and insulator and varies depending on things like temperature or current direction. That is the material used in transistors and diodes.

I would say we are very far away even if this proves to be it.

First you would need to manufacture it reliably, then reliably without impurities, then reliably in some constrained 2d/3d geometry. Then you can start thinking about small footprint applications like IC design (chips and sensors). Perhaps then scale it to PCB design and RF applications like coplanar waveguides.

With that alone you would enter a new era in electronics with virtually no 'thermal noise' and no residual heat.

Beyond that (think large coils, motors, electromagnets) you would need a very large design step. As far as I understand this is still a very brittle ceramic, manufacturing very large or very long chains of this material would be unlikely. So the floating trains are probably a bit further away into the future.

Supposing this lead apatite if conducive, can we not use it for high voltage cables? Some absurd level of energy loss occurs in those.

I understand that there are current limitations inherent in superconductors, but is there no way to scale this?

The cost of losses in the cables may be high, but the cost of superconducting cables may be much higher.

Superconductors may be fragile and unsuitable for cables.

> Some absurd level of energy loss occurs in those.

It doesn't really - because we do the transmission at very high voltage, and the power loss is proportional to 1/V.

Power loss in transmission in the US is about 5%. In the transmission lines themselves it's only 2-4%. [1]

If you ran a power line all the way across the entire continental United States, you'd still get about 80% of the power out of the other end. The longest economically effective distance you can run an AC power line is about 2500mi, and DC around 4300mi. [2]

[1] https://chintglobal.com/blog/how-much-power-loss-in-transmis...

[2] https://en.wikipedia.org/wiki/Electric_power_transmission#ci...

"Depending on voltage level and construction details, HVDC transmission losses are quoted at 3.5% per 1,000 km (620 mi), about 50% less than AC (6.7%) lines at the same voltage."

https://en.wikipedia.org/wiki/High-voltage_direct_current

This seems pretty significant. We don't have much losses because we don't transmit energy over long distances. But now we could.

We definitely do, we just don't want to pay to string up wire thousands of miles, let alone superconducting wire. The difference between keeping 98% of the power that goes through a wire, or 100%, isn't the reason we don't do it. To quantify it further, the current US grid loses 5% to transmission losses which is just less than a cent per kWh.

Most power is generated in a centralized way anyways because it's much more efficient that way. The 'dregs' aren't connected because putting up the wire costs far more than the extra power yields. A few percentage points more efficient won't change the economics, especially if the wire is (a) lead and (b) dramatically more expensive.

3.5% per 1000km is respectfully, basically nothing. You'd get 85% of the power out of a line from SF to NY.

I'm not saying there aren't use cases for room temperature superconductors, I'm saying this is not one that's going to be top of the list.

> 3.5% per 1000km is respectfully, basically nothing. You'd get 85% of the power out of a line from SF to NY.

But why connect SF to NY - what's the advantage? What about connecting a place where it's midnight with a place where it's noon? That'd allow you to use solar arrays instead of local coal/gas/nuclear power plants.

I think you're missing the point of why we make power grids instead of simply having city local generators or stations.

The whole purpose of interconnecting power generation sources is to be able to accommodate for dynamic demand and ensure resiliency.

AC Power networks are sort of similar to how the internet works. The high voltage transmission lines are like the transit lines or "backbone" of the internet.

Those lines connect power stations which are sort of like ISPs in that they deliver the last mile power to the end user.

Our modern society basically instantly stops the second we are unable to meet demand for electricity, so we design these systems in a way where redundancy is supposed to be ensured.

This isn't always the case though. Texas is a great example of a completely messed up electrical grid that is insufficient to support its populous. It causes deaths in heatwaves and freezes almost every year now.

It's not just about transmission losses, though over time those add up. It's also about the cost of the rest of the infrastructure, which is in part because you're dealing with very high voltages and the various step-up/step-down requirements depending on what you're trying to do (long haul, local grid, last mile).

That's included in the 5% number btw. AC transformers are incredibly efficient.

In the loss calculations, not in the capital cost. Transport costs are a function of losses and amortized capital costs (and profits...). A huge part of power grid costs is because of all of the infra dealing with different voltages and transforming between them.

Totally. But I don't think we're anywhere close to knowing what the cost of LK-99 wire is to make a comparison.

That's true, we don't know what it will cost, we're not even sure it can be done at all... But HVDC as it is already in use uses very expensive cable as well so the gap could end up being smaller than you might think at first glance.

https://global-sei.com/technology/tr/bn84/pdf/84-10.pdf

This is state of the art, note the different deployment options, including pressurized ones.

Maybe they will make superconducting transformers instead of cables

One challenge is that these superconductors are ceramic. Brittle and inflexible.

Ceramics materials science has come a long way since the days of clay pots and flexible ceramics are definitely a possibility, depending on how thick you want them to be. Whether that is compatible with superconductivity is of course an open question but I wouldn't rule out a compound that is and superconducting and has a usable bending radius in at least one dimension.

The theory of this particular alleged superconductor is that it's a result of internal stress. I don't think that's compatible with bending.

Internal stress in one direction.

The material on the outside and inside of the bend radius is being stretched and compressed, respectively, along the direction of conduction (assuming any of the anisotropy stuff is more than speculation).

Yes, typically that results in a specific minimum bending radius to ensure material properties are not adversely affected.

This is already done, just not at great scale.

https://en.wikipedia.org/wiki/Superconducting_wire

For detailed information about one actually built and used: https://www.furukawa.co.jp/review/fr035/fr35_04.pdf

The enthusasiam is nice but there's a lot of NIH going on. I'd encourage people to research subject matter before thinking no one else has had similar ideas before.

It's "easy to make" in a sense, but the yields are insanely low (think 1/1000) or less of input materials. This indicates there are some variables that either are not controlled for or cannot be controlled.

That being said, its still early but it looks like LK-99 is not what we typically think about when we think of a super conductor. If we can figure out a good way to make it (with time we likely will), it will still have applications, just likely not high power transmission ones.

I think the financial incentives will speed things up a great deal. Any business that can reliably manufacture it at scale stands to make billions. That usually spurs a lot of innovation.

so a 100 GHz CPU could be not so far away

A 100Ghz CPU would be limited by other factors; mostly c.

That's true, but superconduction would change things from being planar to being cubic and that alone would give a huge boost to speed. Because one main limitation is to be able to get rid of the heat and building 'up' makes that very hard right now.

AFAIK CPU speeds are mainly limited by speed of light already today. There is tradeoff between time to fetch data from L1 cache (or register file), and their size. If you want to fetch the data faster, the cache has to be smaller (or the pipeline will stall), because the signal won't propagate fast enough to the cache. But smaller L1 cache also has negative performance impact, because more data has to be refetched from deeper caches.

Immediate applications for a rtsc would be MRI machines. Those cost between 300k and 500k. They require helium for operation.

A superconductor at room temparature could remove the need for helium or even nitrogen. It could possibly make the machine work with a thermal electric cooler which would drastically lower the upfront cost and the maintenance cost of an MRI. Also, the machine would become smaller which would eliminate the need to roll patients into the machine itself, further reducing costs.

Where a big hospital could only afford one MRI, many small hospitals can now potentially get one for 80k.

I dont know any other existing commercial applications of superconductors.

The resistivity measurements I've seen are 4 wires soldered onto a chunk of material several mm long. If superconducting crystals are growing inside a bulk material, they might be much smaller.

Suppose I had a polycrystalline material with ~ 100 um long superconducting segments. How could I measure the resistance of individual crystals?

It's worth finding small superconducting crystals, because you can probably find ways to make them larger.

4 wire resistive measurements to cancel out the resistivity of the probes is a standard practice[1].

[1] https://www.ni.com/docs/en-US/bundle/ni-daqmx/page/measfunds...

The problem isn't the resistivity of the probes, it's that the probes may not be connected to the same crystal.

I understand the 4 wire idea, but the two inner wires are still farther apart than an individual crystal might be. So a material composed of 100 um superconducting crystals in a resistive bulk medium would appear resistive to probes that are 1 mm apart.

Got it. Building a 4 wire 100um square probe would be doable certainly but not off the shelf.

Where have you seen them soldered? That would be very strange.

https://arxiv.org/pdf/2308.01192.pdf in figure 3.

I'm not sure how they're attached (it looks like gold wire bonding) but the distance is a few mm.

Right, thank you for digging that up. It looks like you are right that is soldered. Either that or wire bonded which is usually a weld, but welding would locally raise the temperature to the point that I wonder if that wouldn't potentially destroy the sample. Given the tiny current I wonder why they didn't use spring loaded contacts, but presumably they know what they are doing and this is just another 'why didn't they' style comment.

So many questions about all of this, I would love to interview all these people, but I totally get that they have much better things to do right now.

First steps of how LK99 could be used - embed superconducting nanocrystals into things. Given how insanely much metals we use for conductors I think it will be quite a while until this sees any kind of mass usage. But wow what an industrial investment boom we would be part of if LK99 actually works.

I also think it is very interesting that this entire class of superconductors will, as far as I can tell, be illegal in the EU for most application due to RoHS:

https://en.wikipedia.org/wiki/Restriction_of_Hazardous_Subst...

The article seems to imply it's re-evaluated regularly (and additive rather than blanket ban although I'm not sure if that's relevant):

> It requires periodic re-evaluations that facilitate gradual broadening of its requirements to cover additional electronic and electrical equipment, cables and spare parts

I’m getting tired of these, mostly because I don’t have the fundamental knowledge to follow or synthesize the significance

is there a youtuber or tiktoker I can follow? even the nerdiest tiktokers know how to communicate effectively so that would be useful right now, far more succinctly than what I’ve seen so far

edit: just searching LK99 on tiktok gets it done

example https://www.tiktok.com/t/ZT8LhJccL/

nothing you couldnt get from a summary anywhere else and these incremental random papers arent easily evaluated or worth your time yet

Just wait for more comments in these threads. Someone knowledgeable is bound to explain more.

The Wikipedia article on LK-99 is not a bad starting point.

I’ve skimmed that as well, its more about the ensuing posts and papers that are equally obtuse and have no update on wikipedia and aren't front page news anywhere

I can’t understand them enough to judge, but is the lack of immediate fanfare from digestible reputable sources an indictment, or am I early? I cant tell where to put energy

They are no more obtuse than your average discussion between a couple of IT people. Welcome to how the rest of the world sees us.

"tiktok gets it done" I'm no physicist but if someone said that about my area of specialization, I'd die a little inside.

Quite.

think about why you need to put energy into this?

do you really care about this or do you just want to win internet points?

there are so many topics in the world, why do you need to put energy into this one?

it's kinda like someone asking which programming language to learn because there are too many of them and all the introduction to programming tutorials are too obtuse and too hard, without a real reason for learning programming in the first place.

like the previous poster said, if you do care about it, the wikipedia article and the footnotes are a good place to start.

well i imagine they would want to put energy into this one for the particular reason that everyone is currently always saying this topic in particular changes basically absolutely everything in the world. but that would be pure speculation on my part.

for me, there are tons of aspects of the world that changes absolutely everything in the world all the time.

medicine, environment, climate effects, stuff that the James Webb Telescope is observing (for example the idea that the universe is way older than we thought), every single moment we are creating or observing something new and suffering from (or benefiting from) the impacts of what we found or created.

If a person wants to go from "I don't know anything about this topic such that a wikipedia article is too confusing to interpret" to "I can understand an arxiv paper and discuss about its significance" they absolutely need to know why they want to do this.

There are a lot of topics in the world, and it's past the time where a DaVinci can master topics from anatomy to physical science to philosophy all in one lifetime. Gotta pick and chose, and knowing why is a big part of picking.

You are just early, the stream of papers are getting posted within hours of their release which is not really enough time to make it to wiki or explainer blogs

I try to post a short summary of why I found a particular article interesting. Not sure it connected this time, but I generally find that helpful when reading someone else’s post from outside my field

If you want to be on the forefront of learning, well, that takes just a tiny bit of effort on your part.

If you don't have the fundamental knowledge, perhaps either stop reading the posts (or keeping reading the posts but don't contribute comments if you don't feel like you have the know how to contribute), OR go and get educated by reading up on the fundamental knowledge needed or taking an general extension course in chemistry and physics, etc if you want to participate.

Nobody is expected to know everything. You don't need to announce to the world that you don't know something. In fact, there is an assumption that if you don't voluntarily post any comments, that you don't know enough about the topic to discuss about it (or just don't care about it).

True. It feels like social media has given many this main charactery need to share their opinion on everything, even if they have nothing to contribute.

Not sure why this is getting such a negative response… it succinctly identifies a challenge in communicating these developments to curious laypersons. Entrepreneurial types like the denizens of Hacker News love the opportunity of a problem they’re positioned to solve, no?

> Not sure why this is getting such a negative response

We're hackers. Newness is enticing. Complaining that you're "getting tired" of something because it's novel while asking for a TikTok summary is lazy.

As another commenter mentioned, start with Wikipedia [1]. From there one sees apatites (think: hydroxyapetite or flurapetite on your teeth) [2]. Searching Google Scholar yields this paper about lead apatite [3][4].

We also see the Wikipedia article talk about diamagnetism; here is a summary video [5]. And here is a promising paper [6] from the Wikipedia entry on quantum wells [7]. I'm currently stuck here: I don't get quantum wells, and don't see--intuitively--how an apatite (or a misformed one) could produce them.

In summary, asking for help is always welcome. Complaining about your ignorance and lack of motivation, seldom so.

[1] https://en.wikipedia.org/wiki/LK-99

[2] https://en.wikipedia.org/wiki/Apatite

[3] https://onlinelibrary.wiley.com/doi/epdf/10.1107/S0567740880...

[4] https://sci-hub.st/https://doi.org/10.1107/S0567740880008096

[5] https://www.youtube.com/watch?v=g0amdIcZt5I

[6] https://ieeexplore.ieee.org/document/8629077

[7] https://en.wikipedia.org/wiki/Quantum_well

I appreciate you trying to help in some way but I didn’t ask anything related to these resources…

Edit: I didn’t read your comment charitably as I should have. The resources are helpful in the broader context and you illustrate that moderate effort can give a layperson some literacy about this.

Still, the root comment contains a perspective worth knowing about. It’s a shame that the commenter is getting dragged for expressing it.

yeah, while having an allergy to the word TikTok misses the point that the appeal is affective communication, something that academics objectively lack. Its about the incentive to communicate succinctly in an engaging way, entire fields and other platforms did not create that incentive and one successfully did. hence, why it is mentioned.

besides that, I appreciate the resources!

I think the problem is that they're on an internet link aggregator complaining they don't understand a topic.

There are means to correct that on the same interface. If he's satisfied that a tikTok video has sated his curiosity, that's fine. But a well-referenced Wikipedia or any number of books or university websites or sciHub skubs will also get you there.

Unless you don't care that much. In which case, why post?

Not every post about a topic should have a handholding first comment. It's fine you don't comprehend the totally of every post, and it serves no one to state the obvious on every post you don't get.

I was exhausted when every fucking post was Haskell and the clear superiority of functional programming, so I just ignored it it read silently.

Even if a conversation seems important, you can simply be silent and absorb information knowing you may want to catch up. The internet functionally contains infinite information about the topic at all levels of explanation.

> Entrepreneurial types like the denizens of Hacker News love the opportunity of a problem they’re positioned to solve, no?

HN denziens also tend to do tech support, and nothing is more triggering than "i tried nothing and am out of ideas"

I'm guessing the negative response was maybe because of the very negative tone.

Somebody submitted what they thought was an interesting link and the comment was dismissive to the point of hostility.

It probably didn't help that the suggestion for a better source of information was TikTok which - while actually having genuinely decent short explainers for all sorts of things - carries with it the stigma of drivel.

Buy a copy of Kittel and read it? His superconductivity chapter is okay enough and only like 50 pages.

I know that's not too helpful, but it's hard to offer much of anything if you don't share what you're struggling with. Or, if you're looking for a Wikipedia-level introduction, I'd suggest... Well, Wikipedia.

I've had success following the rabbit holes of asking questions to ChatGPT (paid, GPT4), which leads to more questions, and so on. It's like following Wikipedia links but I can ask about exact knowledge gaps I have. Eventually some branches of inquiry reach the limits of the model's knowledge and I have to go find an article, but I find having an amateur condensed matter physics tutor in the form of the AI to bounce questions off of speeds things up quite a bit.

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