Room Temperature, Ambient Pressure Superconductivity—This Time for Real?

SCANALYZER The Happening World
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I’ve seen no evidence that the LK-99 results published by the researchers in South Korea (not China, as noted in comment #39 above) were in any way “fake” (indicative of scientific misconduct, deceptive, or intended to defraud). The synthesis process described was complicated and produces heterogeneous material with a variety of properties. The papers reported that some of the material produced exhibited behaviour indicative of superconductivity: sharp decrease in measured electrical resistance below a critical temperature, zero resistance when measured by the best means available, exclusion of magnetic fields (Meissner effect), and change in specific heat near the critical temperature.

The difficulty in producing material which exhibited these properties from the bulk synthesis process led some of the group to explore fabrication by vapour deposition, which might allow better consistency.

This is the process which other researchers have followed in exploring candidates for high temperature superconductivity ever since the discovery of cuprate superconductors in the 1980s. What appears to have happened here is that some of the team jumped the gun and posted a paper on arXiv which inferred superconductivity from the (genuine) results obtained, setting off a global kerfuffle in attempting to reproduce them.

There has been no assertion of which I am aware that any of the results published were fabricated or in any way “fake”, nor is there any credible motive for the researchers involved to falsify data which they obviously knew others would soon independently attempt to replicate.

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See the Wikipedia article “List of Chinese inventions”. The “Four Great Inventions” are usually considered to be:

  • Papermaking
  • Magnetic compass
  • Gunpowder
  • Printing

Other inventions attributed to China include (in alphabetical order):

  • Banknotes (paper money)
  • Belt drive
  • Blast furnace
  • Cannon
  • Cast iron
  • Civil service examinations (meritocratic administration)
  • Crossbow
  • Gas lighting
  • Horse collar
  • Porcelain
  • Rockets
  • Wheelbarrow
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So, some idiot jumps on a hot news story and puts up a fake video hoping for clicks or notoriety—this is news? This happens all the time and, as has been discussed here at length:

is hardly a new phenomenon, and certainly not confined to China.

The implication of comment #38 was that the results reported by the researchers in the papers posted to arXiv and published in Korea were “fake” and that the perpetrators were in China. Both assertions are false and defame what are likely legitimate scientists who jumped the gun or were too enthusiastic about their results. Unlike others with dubious claims to high temperature superconductivity (see the following posts):

the Korean group published data sufficient to reproduce the synthesis of their material, which others around the world promptly performed, made their independent measurements, and confirmed theorists’ models of the material which did not involve superconductivity. This is how science is supposed to work.

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It’s been a bit over a month since the Great Summer Superconductor Flap of 2023 erupted, and since room temperature superconductors are no longer the Current Thing, they’ve largely disappeared from the news. So now, maybe it’s time to start asking:

Room Temperature Superconductivity — Might There Be Something There After All?

I’ve been expecting this to happen. After the rise and fall of “cold fusion” in 1989, sporadic reports of replications and other experiments indicating something anomalous was going on continued for years, with Infinite Energy magazine, amidst breathy reports of “over-unity” devices and zero-point energy, continued to report on work in "low-energy nuclear reactions”. And even now (quoting from the Wikipedia article):

For example, it was reported in Nature, in May, 2019, that Google had spent approximately $10 million on cold fusion research. A group of scientists at well-known research labs (e.g., MIT, Lawrence Berkeley National Lab, and others) worked for several years to establish experimental protocols and measurement techniques in an effort to re-evaluate cold fusion to a high standard of scientific rigor. Their reported conclusion: no cold fusion.

In 2021, following Nature’s 2019 publication of anomalous findings that might only be explained by some localized fusion, scientists at the Naval Surface Warfare Center, Indian Head Division announced that they had assembled a group of scientists from the Navy, Army and National Institute of Standards and Technology to undertake a new, coordinated study. With few exceptions, researchers have had difficulty publishing in mainstream journals. The remaining researchers often term their field Low Energy Nuclear Reactions (LENR), Chemically Assisted Nuclear Reactions (CANR), Lattice Assisted Nuclear Reactions (LANR), Condensed Matter Nuclear Science (CMNS) or Lattice Enabled Nuclear Reactions; one of the reasons being to avoid the negative connotations associated with “cold fusion”. The new names avoid making bold implications, like implying that fusion is actually occurring.

Ahhhh, yes, the Americans forever changing the names of things to avoid notoriety.

Anyway, here we go with room temperature superconductivity. Here is an opening shot from Tom’s Hardware on 2023-08-24.

But the field of superconductors is a fast-changing one. Newly-published, pre-print theoretical research generally continues to support LK-99 as having the properties required to become a superconductor; and now, internet sleuths have discovered a Korean-language update on the original LK-99 patent. This document presents further details (and also new questions) regarding the synthesis process, even as the original Korean authors reaffirm the significance (and veracity) of their discovery.

Unfortunately, what we’re still left with is an incomplete picture of LK-99 - one that will seemingly require much more effort in understanding than some would lead us to believe. But the paper does have what’s required: a graph plotting LK-99’s resistivity. Crucially, the graph says it does drop to zero.

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But it seems that solid state synthesis wasn’t how Lee’s team discovered the (alleged) emergent superconductivity of LK-99. This was done through a technique known as vapor deposition; through it, the same compounds were reacted, but instead of the objective being to end up with an LK-99 crystal, the technique instead allows for the reaction’s vapors to collect against a glass structure, creating a thin film of the compound. According to Sukbae and his team, this film is forged in the 100 degrees Celsius - 400 degrees Celsius temperature range (with a black film of lead sulfide (PbS) in the lower temp area, a white film of lanarkite (Pb2SO5) in the higher temp area, and a gray film of lead appatite in the intermediate area.

It’s from this gray lead-apatite, micron-thick film that the authors insist room-temperature, ambient-pressure superconductivity emerges. The authors also pre-emptively refer state that impurities of iron (Fe) and other elements also emerge from the synthesis process, and that these impurities are well-known sources of ferromagnetism and diamagnetism - some of the features other studies have already encountered and replicated.

But it may have been premature to consider those results as proof that LK-99 is a dud. According to the authors, these magnetic features make it more difficult to see the actual Meissner Effect in action, with less cautious onlookers assuming that LK-99’s levitation capabilities ended at those types of magnetism.

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Which brings us to the latest paper from Vayssilov et al at Sofia University, which also suggests that LK-99 could have the required properties to become a superconductor (do note that once again, there’s no mention of room-temperature or ambient-pressure). The general idea presented in the paper is that there are two ways that could happen: by removing certain oxygen atoms from their places, potential highways for superconductivity appear, with space that was previously occupied by atomic nuclei now being open for electron pairs (the so-called Cooper pairs) to skirt around. Another proposal from the paper is that this same effect can be achieved through the Cu doping we’ve talked about.

Here is the theoretical paper from ChemRxiv, “Alternative Concept of One-Dimensional Superconductivity – Key Role of Defects Revealed by Quantum Chemical Calculations of Lead Apatite” (full text at link). This is the abstract.

Doped lead apatite has been recently reported to feature superconductivity at room temperature and ambient pressure, which may have huge impact on the progress of the humanity in general. The first principle calculations, aiming at understanding the reasons for such behavior, suggest that reduced form of undoped and copper-doped lead apatite contain one dimensional channels, which are free of ions, but with electrostatic potential inside providing conditions for unimpeded electron mobility, potentially leading to superconductivity. Key aspect is that channels are surrounded by lead cations, which generate the necessary electrostatic field but due to their high atomic mass have reduced mobility and do not block the channels even at ambient temperature. Our observations on the modeled structures allowed us to present an alternative concept for features, giving rise of the superconductivity based on chemical understanding of the structure and frontier orbital of the material.

From the start, I found it intriguing that some of the original papers mentioned using vapour deposition as a way to produce uniform material rather than the synthesis process that appears to yield a composite made up of different substances, only some of which exhibit the unusual properties. It will be interesting to see if replications using that (more difficult) technique produce promising results.

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That passage from the article caused me to ignore it when it came out.

The cited document is the KR20230030188 document mentioned in @johnwalker’s original post.

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“Fusion” & “Nuclear” are notorious terms themselves in the context of these technologies which are more like incantations. For all their grounding in theory the engineering of these technologies enjoy, honest names would be “anomalous heat”, “anomalous transmutation” and “anomalous radiation”. Focus on the phenomenology where it belongs when you don’t know what you’re doing and even your measurement instruments are suspect.

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Is LK-99 Superconductivity Back from the Dead?

In a paper was posted on arXiv on 2024-01-02, cautiously titled “Possible Meissner effect near room temperature in copper-substituted lead apatite” (full text at link), nine researchers, eight from China and one from Japan, report experiments with a material similar to the LK-99 in which room-temperature, ambient pressure superconductivity was reported by a Korean laboratory in July 2023. Here is the abstract.

With copper-substituted lead apatite below room temperature, we observe diamagnetic dc magnetization under magnetic field of 25 Oe with remarkable bifurcation between zero-field-cooling and field-cooling measurements, and under 200 Oe it changes to be paramagnetism. A glassy memory effect is found during cooling. Typical hysteresis loops for superconductors are detected below 250 K, along with an asymmetry between forward and backward sweep of magnetic field. Our experiment suggests at room temperature the Meissner effect is possibly present in this material.

Does this indicate there may be a room temperature superconductor lurking in some regions of this notoriously difficult to prepare material? Andrew Côté posted a quick look analysis in a mega-𝕏 post, which I reproduce here as text in the interest of readability and ease of quoting.

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A paper was published this morning by a collaboration of two different teams looking to confirm or invalidate the original LK-99 superconductivity result.

Here’s everything you need to know:

  • A room temperature superconductor would be an invention on-par with the transistor, or perhaps even greater, for its ability to revolutionize every technology that uses electricity.

  • LK99 was a breaking news story last August of a proposed room temperature ambient-pressure superconductor but key measurements failed to be replicated by other laboratories.

  • It was determined that LK-99 was a more mundane diamagnet in a low-strength magnetic field, and developed ferromagnetic properties in a higher magnetic field - it didn’t seem to be a superconductor after all.

Here’s how this current publication stacks up to the previous work on LK99.

Is it the same material? Maybe.

The publication today has a slightly different chemical formulation by the inclusion of Sulfur, whereas previously LK99 did not incorporate this - although the starting ingredients in producing LK99 did include sulfur, and so, sulfur contamination may have been present in the original LK99 sample, but if the original authors thought it wasn’t present, then higher purity replications would’ve missed the mark by cooking up the wrong material.

In other words, that this current material includes sulfur doesn’t rule out that the effect is from the same crystal structure as the original LK99 authors reported (the general name for these materials is ‘lead apatite crystal’ which you will see floating around, like tiny rocks are want to do).

For both the current paper and the original LK99 and its other attempted replications, getting a high purity of the right crystal has always been hard, because the ‘right spot’ for the copper atoms in the crystal is hard for them to reach naturally, i.e. the lowest energy configuration which is the most likely was not though to get the right material properties.

So, the materials produced are low purity, might contain small specks of ‘the right stuff’, and its not completely known which is the right composition or how it works. There have however been simulation studies that don’t rule out such a crystal structure has the right properties believed to explain superconductivity at higher than ultra-low temperatures.

How did the researchers measure superconductivity?

A defining property of superconductors is their ability to perfectly expel an applied magnetic field, up to a limit. This is called the Meissner Effect. If the magnetic field is too strong, the material will fall out of superconducting state and back into a normal conducting state. The field strength at which this happens is called the Critical Field.

Developing superconductors that have a high critical field has been the material science breakthrough which enables the majority of current approaches nuclear fusion, so, it’s a big deal, although the critical field of this sample is fairly small - about 60x the strength of Earth’s field, or 0.2% that of an MRI.

The current publication measurement does the following:

  • Cools the sample down to a low temperature
  • Applies a DC magnetic field
  • Measures the ability to expel this magnetic field, i.e. measures the Meissner effect
  • Sweeps the field strength to find out the critical field

The susceptibility of a magnetic material is how easy it is to become magnetized in the same direction as an applied field. Since a superconductor expels magnetic fields, the susceptibility is negative.

The measurement technique they used is extremely sensitive as is based off a commercial device called an MPMS3 SQUID or Superconducting Quantum Interference Device. This is an extremely mature device built on 40 years of SQUID Magnetometry and can measure down to one part in 10e−8 in terms of sensitivity.

It works by measuring how the expelled magnetic field of a potential superconducting sample interacts with the current traveling in another superconductor circuit called a Josephson Junction (Josephson Junctions are also a fundamental building block of some designs of quantum computers).

Here is probably the most important plot from the paper, showing the ‘Magnetization’ is negative for small field strengths, and this effect is slightly stronger at lower temperatures but still present up to 250K, or about −23C.

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An important consideration here is that there is a ‘memory effect’ involved, where as you sweep the applied field to a low strength, and then back up to a higher strength, you don’t perfectly re-trace the result. This is called Hysteresis and is why there are two lines for a given temperature in the plot.

To understand this, there are actually two types of superconductors, Type-I and Type-II. Type-I will just perfectly expel a magnetic field until you hit the critical field, and then it all falls out of superconducting at once.

Type-II are different and more interesting. When you exceed the critical field strength, the magnetic field penetrates the superconducting material and forms a tiny current loop - the magnetic field aka flux is thought to be ‘pinned’ through the material, and around this ‘pinned flux’ circulates a tiny loop of current known as a vortex. Flux pinning is why Type-II superconductors levitate over a magnet, and the current vortices can influence the measured susceptibility of the sample and generate the hystersis effect, or, memory of past magnetic fields.

Type-I superconductors therefore always have a susceptibility of -1, while Type-II can have susceptibilities that are negative fractions, i.e. -0.3, as seen in the graph.

An oddity I will point out is their device, the MPMS3 SQUID Magnetometer, is also capable of performing a measurement technique called AC Susceptibility which is usually better at picking out superconducting from small grains in an impure sample, but the authors instead used DC Susceptibility. I’m not sure why they didn’t also run the AC Susceptibility test.

What’s the Net-Net?

The authors are careful to say this is a ‘Possible Meissner effect’ and that it is ‘near room temperature’ - which is wise. Last August, there was a lot of hype and a flurry of scientific interest, which didn’t pan out.

Scientists have to be very cautious to get things right and not over-state their claims, since their industry largely runs on reputation of credibility to be taken seriously by others in the scientific community.

It therefore makes sense that after last August, most people will treat this with a lot of caution, perhaps dismiss it entirely, or at least not engage with as much interest and fervor as last time.

The likeliest outcome here is that Lead Apatite Crystals just have some weird magnetic properties at low field strengths, and experience a transition in properties at near-room temperatures.

A much more exciting but lower-odds outcome is that Lead Apatite Crystals end up providing a fruitful line of research that develops room temperature superconductors, which means we don’t need to invade that planet from Avatar for unobtanium - we can produce it in bulk from some of the most common elements on Earth - Copper, Oxygen, Lead, and Sulfur.

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