Ambient Temperature/Pressure Superconductors

[Recusant]

There was a claim made a few months ago that wasn't really borne out (one paper already retracted, a second likely to be retracted). Now another comes along, from a completely different team. Not peer reviewed yet, so don't hold your breath. However, it would be a significant development, potentially changing our technology in amazing ways.

"A room-temperature, ambient-pressure superconductor? Take a closer look" | The Register

Three scientists in South Korea claim they've crafted a superconductor that works at both room temperature and ambient pressure – a revolutionary breakthrough if confirmed.

Superconductors – which are able to conduct electricity with virtually no resistance, and therefore have almost zero energy loss – typically require intense cold and pressure to function. In a pre-print paper, the scientific trio state they were able to produce a modified form of lead-apatite dubbed LK-99 that is superconductive at any temperature below 127°C (261°F) without the need for pressure chambers.

Such a superconductor could be useful, provided all of its physical characteristics are sound. For example, it could be used to make faster digital electronics, resulting in higher performance from personal computers. It could be used in MRI machines without the extreme cooling required, which has caused a shortage of helium. Something like LK-99 could replace the powerful magnets in maglev trains and fusion reactors. And obviously could produce super-efficient power transmission lines.

[. . .]

"All evidence and explanation lead that LK-99 is the first room-temperature and ambient-pressure superconductor," the trio claimed in their paper.

"We believe that our new development will be a brand-new historical event that opens a new era for humankind." Not to overstate things.

As far as we're aware, their study has not yet been accepted or published in a peer-reviewed journal. We've asked them for further comment.

[. . .]

The Register reached out to several physics departments and labs to get their take on the LK-99 paper, and we'll let you know what they make of it all. Professors Susannah Speller and Chris Grovenor of the University of Oxford's Department of Materials in England earlier told the i newspaper they have some doubts about the South Korean team's claims.

"It is too early to say that we have been presented with compelling evidence for superconductivity in these samples," the duo said. They added the paper was interesting, though the results weren't wholly convincing.

Two critical data points needed to ascertain the superconductivity of LK-99 – its magnetization changing as well as heat capacity – aren't evident in the data the trio presented, Profs Speller and Grovenor argued.

Another physicist, Sven Friedemann of the University of Bristol in England, shared that assessment, saying vital evidence was missing from the South Korea paper. Friedemann also questioned whether footage in the study claiming to show Meissner effect levitation due to expulsion of magnetic fields could be also caused by a non-superconducting source.

So hold the excitement, for now at least.

[Continues . . .]

The paper is available as a pre-print.

"The First Room-Temperature Ambient-Pressure Superconductor" | arXiv

For the first time in the world, we succeeded in synthesizing the room-temperature superconductor (T_c≥400 K, 127∘C) working at ambient pressure with a modified lead-apatite (LK-99) structure. The superconductivity of LK-99 is proved with the Critical temperature (T_c), Zero-resistivity, Critical current (I_c), Critical magnetic field (H_c), and the Meissner effect.

The superconductivity of LK-99 originates from minute structural distortion by a slight volume shrinkage (0.48 %), not by external factors such as temperature and pressure. The shrinkage is caused by Cu²+ substitution of Pb²+(2) ions in the insulating network of Pb(2)-phosphate and it generates the stress.

It concurrently transfers to Pb(1) of the cylindrical column resulting in distortion of the cylindrical column interface, which creates superconducting quantum wells (SQWs) in the interface. The heat capacity results indicated that the new model is suitable for explaining the superconductivity of LK-99. The unique structure of LK-99 that allows the minute distorted structure to be maintained in the interfaces is the most important factor that LK-99 maintains and exhibits superconductivity at room temperatures and ambient pressure.

[Icarus]

I read about this a few months back. I expected a great deal of media attention to the claimed breakthrough. No such excitement was forthcoming. Now a new set of claims.

Let us hope that the Korean guys have developed something as spectacular as room temperature superconductors. Skepticism abounds for now.

[Tank]

Fingers crossed this is it. Can you imagine rechargeable batteries that can be recharged in seconds?
 

[Recusant]

Back to the drawing board. Seems it has been more or less conclusively determined that LK-99 is not a room-temperature superconductor. 

"LK-99 Is No Radical Superconductor After All, Scientists Confirm" | | Science Alert

Ever since the spooky phenomenon of superconductivity was discovered in 1911, scientists have been searching for superconducting materials that work under practical conditions.

If only they could find a compound in which electrical resistance vanishes at room temperature and ambient pressure – not extreme cold and ultrahigh forces – then we could finally step into the world they envisage of ultrafast computer chips, levitating trains, and superefficient energy grids.

For a hot minute, it looked like 2023 was going to be the year where physicists' pursuits broke through the room-temperature barrier. But those hopes – which were doused in skepticism from the start – were dashed not once, but twice in the space of a few months.

Now, the findings from a team of materials scientists at the Chinese Academy of Sciences (CAS) have been peer-reviewed, putting another nail in the coffin of LK-99, the material a South Korean team claimed in July was a room-temperature superconductor.

[. . .]

To recap, Zhu and colleagues synthesized two kinds of LK-99 with different copper(I) sulfide (Cu₂S) content and investigated the samples' material properties.

Firstly, they showed the electrical resistance of Cu₂S alone plummeted around 112 °C (385 K) and they saw a similar effect in LK-99 samples with lots of copper sulfide impurities.

That 'transition' temperature is not far off 105 °C – the temperature at which the South Korean team reported LK-99's superconductivity properties emerged.

But Zhu and colleagues argue that LK-99's superconductor-like properties most likely originate from the Cu₂S, which morphs from a hexagonal structure to a monoclinic one near 126 °C (400 K). Their impure LK-99 samples also didn't show zero resistivity like a true superconductor would.

This "strongly suggests that the superconductivity-like behavior in LK-99 reported by Lee et al. is caused by the structural phase transition of the impurity Cu₂S" the researchers write.

[Continues . . .]

A pre-print version of the paper (which has now been peer-reviewed and published in Matter) is open access:

"First order transition in Pb10-xCux(PO4)6O (0.9<x<1.1) containing Cu₂S" | arXiv

Abstract:

Lee et al. reported that the compound LK-99, with a chemical formula of Pb10xCux(PO4)6O (0.9<x<1.1), exhibits room-temperature superconductivity under ambient pressure. In this study, we investigated the transport and magnetic properties of pure Cu₂S and LK-99 containing Cu₂S.

We observed a sharp superconducting-like transition and a thermal hysteresis behavior in the resistivity and magnetic susceptibility. However, we did not observe zero-resistivity below the transition temperature. We argue that the so-called superconducting behavior in LK-99 is most likely due to a reduction in resistivity caused by the first order structural phase transition of Cu2S at around 385 K, from the β phase at high temperature to the γ phase at low temperature.

[Tank]