Evidence For Graphite As A Room Temperature Superconductor

February 6, 2024 by Maya Posch 30 Comments

Magnetization M(H) hysteresis loops measured for the HOPG sample, before and after 800 K annealing to remove ferromagnetic influences. (Credit: Kopelevich et al., 2023)

Little has to be said about why superconducting materials are so tantalizing, or what the benefits of an ambient pressure, room temperature material with superconducting properties would be. The main problem here is not so much the ‘room temperature’ part, as metallic hydrogen is already capable of this feat, if at pressures far too high for reasonable use. Now a recent research article in Advanced Quantum Technologies by Yakov Kopelevich and colleagues provides evidence that superconducting properties can be found in cleaved highly oriented pyrolytic graphite (HOPG). The fact that this feat was reported as having been measured at ambient pressure and room temperature makes this quite noteworthy.

What is claimed is that the difference from plain HOPG is the presence of parallel linear defects that result from the cleaving process, a defect line in which the authors speculate that the strain gradient fluctuations result in the formation of superconducting islands, linked by the Josephson effect into Josephson junctions. In the article, resistance and magnetization measurements on the sample are described, which provide results that provide evidence for the presence of these junctions that would link superconducting islands on the cleaved HOPG sample together.

As with any such claim, it is of course essential that it is independently reproduced, which we are likely to see the results of before long. An interesting part of the claim made is that this type of superconductivity in linear defects of stacked materials could apply more universally, beyond just graphite. Assuming this research data is reproduced successfully, the next step would likely be to find ways to turn this effect into practical applications over the coming years and decades.

Hackaday Links: August 13, 2023

August 13, 2023 by Dan Maloney 14 Comments

Remember that time when the entire physics community dropped what it was doing to replicate the extraordinary claim that a room-temperature semiconductor had been discovered? We sure do, and if it seems like it was just yesterday, it’s probably because it pretty much was. The news of LK-99, a copper-modified lead apatite compound, hit at the end of July; now, barely three weeks later, comes news that not only is LK-99 not a superconductor, but that its resistivity at room temperature is about a billion times higher than copper. For anyone who rode the “cold fusion” hype train back in the late 1980s, LK-99 had a bit of code smell on it from the start. We figured we’d sit back and let science do what science does, and sure enough, the extraordinary claim seems not to be able to muster the kind of extraordinary evidence it needs to support it — with the significant caveat that a lot of the debunking papers –and indeed the original paper on LK-99 — seem still to be just preprints, and have not been peer-reviewed yet.

So what does all this mean? Sadly, probably not much. Despite the overwrought popular media coverage, a true room-temperature and pressure superconductor was probably not going to save the world, at least not right away. The indispensable Asianometry channel on YouTube did a great video on this. As always, his focus is on the semiconductor industry, so his analysis has to be viewed through that lens. He argues that room-temperature superconductors wouldn’t make much difference in semiconductors because the place where they’d most likely be employed, the interconnects on chips, will still have inductance and capacitance even if their resistance is zero. That doesn’t mean room-temperature superconductors wouldn’t be a great thing to have, of course; seems like they’d be revolutionary for power transmission if nothing else. But not so much for semiconductors, and certainly not today.

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LK-99: Diamagnetc Semiconductor, Not Superconductor?

August 5, 2023 by Jenny List 70 Comments

Every so often, along comes a story which, like [Fox Mulder] with his unexplained phenomena, we want to believe. EM drives and cold fusion for example would be the coolest of the cool if they worked, but sadly they crumbled when subjected to scientific inquiry outside the labs of their originators. The jury’s still out on the latest example, a claimed room-temperature superconductor, but it’s starting to seem that it might instead be a diamagnetic semiconductor.

We covered some of the story surrounding the announcement of LK-99 and subsequent reports of it levitating under magnetic fields, but today’s installment comes courtesy of a team from Beihang University in Beijing. They’ve published a paper in which they characterize their sample of LK-99, and sadly according to them it’s no superconductor.

Instead it’s a diamagnetic semiconductor, something that in itself probably bears some explanation. We’re guessing most readers will be familiar with semiconductors, but diamagnetic substances possess the property of having an external magnetic field induce an internal magnetic field in the opposite direction. This means that they will levitate in a magnetic field, but not due to the Meissner effect, the property of superconductors which causes magnetic field to flow round their outside. The Beijing team have shown by measuring the resistance of the sample that it’s not a superconductor.

So sadly it seems LK-99 isn’t the miracle it was billed as, unless there’s some special quirk in the production of the original Korean sample which didn’t make it to the other teams. We can’t help wondering why a sample from Korea wasn’t subjected to external evaluation rather than leaving the other teams to make their own. Never mind, eh!

“Room Temperature Superconductor” LK-99, Just Maybe It Could Be Real

August 1, 2023 by Jenny List 66 Comments

To have been alive over the last five decades is to have seen superconductors progress from only possible at near-absolute-zero temperatures, to around the temperature of liquid nitrogen in the 1980s and ’90s, and inching slowly higher as ever more exotic substances are made and subjected to demanding conditions. Now there’s a new kid on the block with an astounding claim of room-temperature and pressure superconductivity, something that has been a Holy Grail for physicists over many years.

LK-99 is a lead-copper-phosphate compound developed by a team from Korea University in Seoul. Its announcement was met with skepticism from the scientific community and the first attempts to replicate it proved unsuccessful, but now a team at Huazhong University of Science and Technology in China claim to have also made LK-99 samples that levitate under a magnetic field at room temperature and pressure. This is corroborated by simulation studies that back up the Korean assertions about the crystal structure of LK-99, so maybe, just maybe, room temperature and pressure superconductors might at last be with us.

Floating on a magnetic field is cool as anything, but what are the benefits of such a material? By removing electrical resistance and noise from the equation they hold the promise of lossless power generation and conversion along with higher-performance electronics both analogue and digital, which would revolutionize what we have come to expect from electronics. Of course we’re excited about them and we think you should be too, but perhaps we’ll wait for more labs to verify LK-99 before we celebrate too much. After all, if it proves over-optimistic, it wouldn’t be the first time.