Floating trains and limitless electricity: The mystery of superconductivity

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Since its discovery over a century ago, superconductivity has proved to be one of the most mysterious phenomena in all of science. Despite its extensive study, physicists and chemists still have more questions than answers, and the possibility of creating room-temperature superconductors has driven some of the best minds on the planet to fervent pursuit of a solution.

So what is superconductivity? Put simply, it is a property of materials that allows electricity to flow with zero resistance below a specific transition temperature. It was originally discovered serendipitously by a German physicist named Heike Kamerlingh Onnes in 1908 whilst he was studying the resistance of mercury at temperatures near absolute zero.

It did not take long for the global scientific community to take notice, but it became quickly apparent that there would be no immediate explanation. Over the last century, a string of breakthroughs and the gradual development of theory has added to our understanding, but many question marks still remain.

In the 1950s, three scientists – John Bardeen, Leon Cooper and Robert Schrieffer – published their BCS theory which described the delocalised electrons in metals joining up to form “Cooper Pairs”. This theory was reinforced by the work of a Soviet scientist of the same period called Lev Landau, although he used a completely different approach.

This theory was hailed as a huge success and eventually won its creators a Nobel Prize. After this, it was felt that little more would come from research into superconductors – BCS theory predicted superconductors which operated at temperatures over about 25K (25C above absolute zero) could not exist.

But, three decades later, everything changed. Of the relatively few scientists who were still looking for high-temperature superconductors, most were interested in metallic alloys. Yet, in 1986, it was Georg Bednorz and Alex Müller, instead choosing to pursue oxides, who developed a superconductor which could work at about 30K (-243C).

This finding upturned all previous understanding of superconductors and generated a sudden flurry of activity in the field. Through experimentation with various different compounds, scientists have gradually but steadily pushed transition temperatures higher and higher, and today the record stands at an impressive 203K (-70C).

Producing superconductors that work at room temperature now seems a lot more feasible, and this idea has led to much speculation about possible applications.

Superconductors are already used in lots of different places. For instance, Japan’s magnetic levitation (Maglev) train near Yamanashi broke the world speed record, which it had previously set itself, travelling at 374 mph, in April 2015.

Maglev trains exploit the Meissner effect that superconductivity produces to levitate the vehicle above the track and propels it forward with magnets. Due to no resistance save that of the air, these trains can reach extremely high speeds.

Superconductors can also help to make extremely powerful magnets which can be used in MRI scanners, or in particle accelerators such as those at CERN. There is even research being done on the possibility of building superconducting quantum computers.

Unfortunately, the low temperatures still mean a lot of energy and money is wasted due to the costs of cooling. But if we could produce a room-temperature superconductor, this technology could be used all over the world to carry out work at no cost. It seems almost too good to be true.

Although at the moment there is no clear way to achieve this holy grail in material science, and many doubt we will ever find a room-temperature superconductor, what is unquestionable is the fact that the history of superconductivity is existing evidence that we can never rule out any eventuality, as unlikely as it may seem.