Ever because the spooky phenomenon of superconductivity was discovered in 1911, scientists have been searching for superconducting materials that work underneath sensible situations.
If solely they might discover a compound during which electrical resistance vanishes at room temperature and ambient strain – not excessive chilly and ultrahigh forces – then we might lastly step into the world they envisage of ultrafast pc chips, levitating trains, and superefficient vitality grids.
For a sizzling minute, it appeared like 2023 was going to be the 12 months the place physicists’ pursuits broke through the room-temperature barrier. However these hopes – which had been doused in skepticism from the beginning – had been dashed not once, but twice within the area of some months.
Now, the findings from a workforce of supplies scientists on the Chinese language Academy of Sciences (CAS) have been peer-reviewed, placing one other nail within the coffin of LK-99, the fabric a South Korean team claimed in July was a room-temperature superconductor.
Should you’ve been following the LK-99 saga, you will have been by means of a rollercoaster of feelings the previous few months as scientists scrambled to replicate the South Korean workforce’s extraordinary claims – and had been in the end left wanting.
LK-99 consists of copper, lead, phosphorus and oxygen, and the South Korean workforce claimed (in two preprints, neither peer-reviewed) that {the electrical} resistance of the fabric dropped sharply because it cooled from a slightly toasty 105 °C (378 Ok).
Close to-zero resistance is one of two key properties of superconductivity; the opposite being the way in which magnetic fields are expelled from superconducting supplies in what’s often called the Meissner effect, inflicting them to levitate above magnets.
A series of preprints printed simply weeks after the information of LK-99 first broke introduced these claims about LK-99’s purported superconductivity crashing again right down to Earth.
One preprint describing LK-99’s chemical structure mentioned that construction made superconductivity infeasible. Different experiments suggested ferromagnetism, not superconductivity, was behind LK-99’s off-kilter, partial levitation.
A 3rd preprint, from Shilin Zhu and colleagues on the CAS Institute of Physics, prompt LK-99’s purported superconductive properties had been really as a result of impurities in the material – specifically, copper(I) sulfide. That examine has now been peer-reviewed, including weight to its conclusions.
“A surge in misleading information about LK- 99 call[ed] for urgent clarification of its superconductivity,” the researchers write.
To recap, Zhu and colleagues synthesized two sorts of LK-99 with completely different copper(I) sulfide (Cu2S) content material and investigated the samples’ materials properties.
Firstly, they confirmed {the electrical} resistance of Cu2S alone plummeted round 112 °C (385 Ok) and so they noticed an identical impact in LK-99 samples with a number of copper sulfide impurities.
That ‘transition’ temperature shouldn’t be far off 105 °C – the temperature at which the South Korean workforce reported LK-99’s superconductivity properties emerged.
However Zhu and colleagues argue that LK-99’s superconductor-like properties most certainly originate from the Cu2S, which morphs from a hexagonal construction to a monoclinic one close to 126 °C (400 Ok). Their impure LK-99 samples additionally did not present zero resistivity like a real 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.
Quickly after Zhu and colleagues shared these findings as a preprint in August, different researchers not concerned within the work told Nature they thought issues had been “pretty decisively settled” and LK-99 was not a room-temperature superconductor.
Now that Zhu and colleagues’ findings have handed peer review, it could appear extra researchers agree.
The examine has been printed in Matter.
