“We unleashed an avalanche,” said K. Alex Müller on the 20th anniversary of the discovery of high-temperature superconductivity, for which he and fellow scientist J. Georg Bednorz won the Nobel Prize in 1987. The award-winning researcher died at the start of this year at the age of 95 – and the avalanche triggered by him and his colleague is yet to settle.
On the contrary: this summer, news from South Korean researchers about a superconductor that doesn’t need to be cooled surprised the scientific community. The dubious material called LK-99, which could apparently conduct electricity without loss at room temperature, created a buzz of excitement – stoked by a striking image on social media showing a floating sample.
However, countless attempts to reproduce the experiment have come to naught, and experts now believe that the apparent superconductivity of LK-99 was a false positive. The hype around the alleged breakthrough shows the great fascination that still surrounds superconducting materials. “The possibility of transporting electricity without loss is something anyone can grasp and everyone finds exciting,” says Andreas Schilling, professor of experimental physics at the University of Zurich.
Schilling is following in the footsteps of the late K. Alex Müller by researching superconductors. He does not use the materials that Müller and Bednorz used in their time, however, but has moved on to other compounds. Schilling is one of the speakers at the 21 September symposium (in german), which will focus on the late Nobel laureate and feature appearances by his close colleagues and significant figures from the scientific community. In addition, from September 19 to October 14, an exhibition in the Irchel Lichthof will offer insights into the life of the researcher and the world of high-temperature superconductivity.
Time to make a call to Georg Bednorz at his home in Wolfhausen in the Zurich Oberland region. Now retired, the physicist can no longer be reached at the IBM research center in Rüschlikon, where he worked for many years. A hearty voice answers the phone; Bednorz speaks quickly and with firm conviction.
Of course he still recalls the events of 1983, when he and K. Alex Müller began carrying out experiments to search for high-temperature superconductivity in ceramics. At that time Müller was head of the physics department at the IBM research lab and a professor at UZH while Bednorz was an associate in another research group. The two men were well acquainted, as Müller had been Bednorz’s doctoral thesis supervisor. For years, they kept the superconductivity experiments they were running alongside other projects quiet.
“That was purely a protective measure,” Bednorz says, “because we feared that our venture would be dismissed as absurd in scientific circles.” Prevailing opinion at the time doubted ceramics could be superconductors. “But certain theoretical considerations led us to ceramics with nickel or copper oxide.”
After three years of experimenting and testing, the hoped-for success came in 1986. Thanks to a compound of barium, lanthanum and copper oxide, the two researchers were able to raise the transition temperature below which electrical resistance collapses by 12 degrees to -238 degrees Celsius. At the time, it was the highest temperature ever measured for superconductivity.
“At first no one believed us,” recalls Georg Bednorz. Japanese research groups were the first to take up the duo’s experiments and try to reproduce the results. As the findings were gradually confirmed, the above-mentioned avalanche was set in motion.
Physicists far and wide began experimenting with superconducting compounds based on copper oxides and were soon able to raise temperatures to -180 degrees Celsius. This made it possible to use liquid nitrogen, which has a boiling point of -196 degrees Celsius, to cool the materials – a huge advance over the previously required liquid helium, which has a boiling point of -269 degrees Celsius but is much more expensive.
The glorious confirmation and continuation of Bednorz’s and Müller’s work paved the way for their Nobel Prize, which was awarded just one year after the groundbreaking experiments in 1987, for “an important breakthrough in the discovery of superconductivity in ceramic materials,” according to the Nobel Prize committee’s tribute.
In 1987, Andreas Schilling was part of Hans Rudolf Ott’s research group at ETH Zurich and was also experimenting with copper oxides. He can lay claim to having discovered the material with the highest transition temperature for copper oxides, which is now -138 degrees Celsius. “Higher temperatures could not be reached with this material under normal conditions,” says Andreas Schilling.
Almost 40 years have passed since the memorable experiments. What practical applications have the findings led to in the meantime? Georg Bednorz admits that the innovation does not have much practical application in everyday life.
In Switzerland, high-temperature superconductivity is mainly used in research settings – at CERN, for example. The electrical leads of the Large Hadron Collider particle accelerator’s magnets are based on high-temperature superconductors. Since 2008, these ceramics have been transporting massive amounts of electricity of 13,000 amperes almost loss-free.
“The technology works reliably, as other examples show,” says Bednorz. “Whether it will be used more is a question of political will.” For example, in the German town of Essen tests have been successfully carried out on the urban network using superconductors one kilometer in length. Considerably longer cables are being developed. A wind power plant in Denmark has also successfully tested a generator with coils made of superconducting wires for the first time.
Bednorz’s conviction is palpable: “With the necessity of transforming the energy supply away from fossil fuels, the hour of superconductivity has come.” Wherever electricity is generated and transported or converted into magnetic fields, superconductors increase efficiency and performance. The researcher is adamant: “The future is electric. If there’s no will to deploy this technology now, then when?!”
If there’s no will to deploy the technology of superconductivity now, then when?!
It remains to be seen whether the decarbonization of the energy industry will lead to the widespread use of superconductivity as Georg Bednorz would like. But a different aspect of this memorable Nobel Prize is crystal clear, one which research policymakers should take to heart.
The two physicists had the courage to come up with unconventional ideas and to swim against the current. Thanks to their perseverance and a bit of luck (always part of it, notes Bednorz), they were successful. “This success was only possible because the IBM institute gave them complete freedom to take risks,” says Andreas Schilling. This freedom is what enabled Georg Bednorz and K. Alex Müller to forge their own path and bring about a paradigm shift.