 "Superconductors")
In late July, a group of South Korean scientists claimed they had developed a lead-based compound, LK-99, which displayed superconducting properties at room temperature and normal pressure conditions. The scientists from the Quantum Energy Research Centre said that LK-99 is a material made up of lead, copper, and phosphorus.
The claims led to unprecedented excitement among experts in the field and also triggered scepticism in the scientific community. But what is a room-temperature superconductor? And why is this claim making news?
What is a superconductor?
A superconductor is a material that conducts electricity with almost 100 per cent efficiency. This means that the material offers no resistance to electricity, thereby preventing any energy loss in the form of heat, sound or other forms of energy. Simply defined, a superconductor is a material that offers electrical current zero resistance.
Superconductivity is a condition in which electrical resistance drops to zero. It can be achieved only under extremely low temperatures or high-pressure conditions.
The importance of low temperature
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Some metals become superconductors under extremely low temperatures. The temperature at which the resistance drops to zero is known as the critical temperature.
For aluminium, the critical temperature is 1.2 Kelvin (or -271.9 degrees Celsius). Indium attains superconductivity at 3.4 K (-269.75 degrees Celsius). Mercury at 4.2 K (-268.95 degrees Celsius) and Lead at 7.2 K (-265.95 degrees Celsius).
But what if there was a superconductor that did this at room temperature? The search for such superconductors is one of the holy grails of materials science. Till now, the search for such material has proved elusive.
This is the reason the claims by the South Korean scientists regarding LK-99 have made the scientific world sit up.
How will room-temperature superconductors impact the future?
Superconductor technology like LK-99 could lead to a tectonic shift in the fields of power and transportation. Such a material could lead to a new age of frictionless high-speed trains, lossless power lines and super-efficient quantum computers. Particle accelerators and nuclear fusion devices could also be run in a cost-efficient manner.
Superconducting materials are already in use in a variety of applications around the world, such as MRI machines, but they require extremely low temperatures or extremely high pressures. Such conditions are difficult and expensive to maintain.
Despite many previous claims about room-temperature superconductors falling flat, the prospect of discovering such material has motivated researchers to push forward.
How do superconductors work?
At normal temperatures, all materials offer some amount of electrical resistance. Modern materials that are used to conduct electricity, like wiring supplying energy to homes, are inefficient. As electrons move from one end of the wire to the other, they keep bumping into atoms and are slowed, creating heat and causing energy to be lost. But if wires were to be made from a superconductive material, these losses could be nullified.
The nuclei of all atoms vibrate at a constant rate. In a superconducting material, the electrons move from atom to atom in a coordinated way, in sync with the vibrating nuclei. This efficient movement leads to no collisions; therefore, there is no resistance to the flow of electricity. The movement of electrons and nuclei becomes more organised at colder temperatures. Hence, the existing crop of superconductors only works at extremely low temperatures.
Why the need for a room-temperature superconductor?
Since the electric current flowing through metal wire suffers losses due to the wire's electrical resistance, a significant amount of electricity is lost in transmission. Scientists have pondered the existence of materials that would offer no resistance to the flow of electricity.
Such superconducting materials were discovered more than a century ago. In 1911, Dutch physicist Heike Kamerlingh Onnes discovered that mercury, a liquid metal at room temperature, becomes a superconductor at an extremely cold temperature of -268.95 degrees Celsius. Such temperatures at which materials such as lead, aluminium, tin, niobium, and several others become superconductors are known as critical temperatures. In the late 1970s, scientists believed that superconductors couldn't function at more than -240 degrees Celsius.
After several years of research, scientists concluded that superconductivity in metals could be achieved if they can be cooled down to suitably low temperatures.
Researchers also realised that along with being perfect conductors of electricity, superconductors also have many other properties that could lead to monumental breakthroughs in the fields of energy, transportation and computers.
Hence, the challenge before scientists has been to discover a material that can conduct electricity without resistance at an ordinary temperature and pressure.
Controversy over LK-99
Scientists have expressed doubts about the claims of the South Korean researchers as several versions of the LK-99 paper have appeared on the preprint platform arXiv with inconsistent data, and their findings have not been put through basic tests used to confirm superconductivity.
Critics said the research paper is waiting to be peer-reviewed for publication and contains low-quality data.
The Korean Society of Superconductivity and Cryogenics stated that it had asked the Quantum Energy Research Centre to submit samples to verify its researchers' findings of a room-temperature superconductor material, Reuters reported on Thursday.
"Based on data from the two archived papers and the video made public, the materials ... cannot be called room temperature superconductors at this point," the group said.
Recent claims of room-temperature superconductivity have been met with scepticism, as none of them has been able to withstand rigorous scientific scrutiny. In July, Physical Review Letters, a prominent scientific journal, decided to retract a paper by Ranga Dias, a physicist at the University of Rochester, apparently because of faulty data. Nature retracted another paper by Dias in September last year after researchers could not reproduce the results.
