New frontier. Is superconductivity finally within reach?

A new material, synthesised by a group of Korean scientists, has brought superconductivity tantalisingly within reach. The compound, which the scientists have named “LK-99”, has become the talk of the scientific world and the potential to fetch them the Nobel Prize, for it cracks a problem that physicists have been racking their brains over for 110 years.

Caution: Superconductivity is not yet in our hands; it is just very close. But first, some background about ‘superconductivity’.

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There is no better way to describe “superconductivity” than to use a cliché: holy grail of scientists. When you send electricity across a wire, a little bit of it gets wastefully converted to heat, because of the phenomenon called ‘resistance’. We call ‘transmission and distribution losses’, or T&D. In India, a fifth of the electricity generated disappears into this T&D loss crack.

But if resistance is removed, then electricity will zip through the wires without any T&D loss. You can remove resistance only if you can cool the wires to extremely cold temperatures. Different materials need to be cooled to different temperatures for superconductivity. For example, copper needs to get down to near absolute zero (-273 degrees C) for it to become superconducting. Some other materials, such as lead and some alloys of titanium, become superconducting at –243 degrees C.

For well over half a century, scientists have been trying to concoct a material that can conduct electricity without a part of the energy getting wasted as heat—while operating at either room temperature or, at least, not so low temperatures. Research in ‘high temperature superconductivity’ is keenly watched because the benefits of superconductivity are immense. Line losses will come down drastically. With super conducting wires in them, motors and generators can be much smaller, which in turn have huge economic implications. For example, the cost of offshore wind energy could come down with only smaller turbines needed.

Enter LK-99

Sukbae Lee, Ji-Hoon Kim (hence, ‘LK’) and Young-Wan Kwon of the Korea University, Seoul, who have been working on superconductivity for two decades, recently produced a scientific paper, in which they said they had synthesised a lead apatite compound which showed superconducting characteristics at room temperature. The material retained superconducting property up to a temperature of 127 degrees C. “For the first time in the world, we succeeded in synthesising the room-temperature superconductor working at ambient pressure with a modified lead-apatite (LK-99) structure,” is how the paper begins.

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“If this is true, then the world will change in ways that you cannot imagine,” says Prof Deepshikha Jaiswal Nagar, Associate Professor (Physics), Indian Institute of Science Education and Research, Thiruvananthapuram.

The paper has stirred things up in the scientific world. At least two groups of scientists tried to replicate what the Koreans did—in vain. Synthesising LK-99 was no big deal—anyone apparently can do it following the Koreans’ recipe. One group was led by Dr Veer Awana of National Physical Laboratories, New Delhi, and the other was a Chinese group. Alongside, Prof G Baskaran, Distinguished Professor, Department of Physics, IIT-Madras, got busy trying to provide theoretical explanation for the Korean experiments.

Both Dr Awana and the Chinese group were unable to get the same results as the Koreans, meaning, LK-99 failed on the test of replicability. They were not able to get the ‘diamagnetism’ in the sample they tried out. A superconducting material must have two defining characteristics.: It must offer no resistance to the flow of current and must become diamagnetism—which means, it must repel magnets. If you put a magnet above it, the magnet must levitate—the broad principle behind maglev trains. The Indian and Chinese groups did not get the diamagnetic property in their LK-99 sample.

However, this is not the end of the story. “The compound (LK-99) has not been proven yet, but is very promising,” Dr Awana told businessline on Thursday. Asked if there was still scope for optimism, he said, “100 per cent”.

Why could the Koreans get superconductivity in LK-99 but not the others? Theoretical physicists have provided a clue. Basically, LK-99 is a compound of lead and copper, in which the lead is in a cylindrical structure and copper runs around it like a chain. To put it in simple terms, there are two “sites” in lead where copper can plug in. In the material the Koreans developed, copper plugged in at site-2, whereas in that of the Indians and the Chinese, it was at site-1. Doping at the wrong site probably explains why the Koreans are rejoicing while the others are wringing their hands. Whether it was by a stroke of luck that the Koreans got their doping right or by design is not clear as yet.

Regardless, LK-99 has heightened interest in superconductivity. “LK-99, till date, is the most promising material,” Dr Awana said. In his lab, he is working on using zinc in the place of copper, hoping for better results. “The sample is in the furnace,” he said.

This is not the first-time laboratory success in superconductivity has been claimed. A few years ago, there was a famous, controversial claim of the lab of Ranga Dias of the University of Rochester, New York. Regardless of whether such claims were mendacious or honest, they all claimed superconductivity at extremely high pressures. In the case of LK-99, no pressure was applied, which is what makes it so attractive.