EuroWire January 2020

Transatlantic Cable

Superconductivity that resists magnetism Strong magnetic fields destroy the superconducting state in the vast majority of materials. In uranium ditelluride, however, a strong magnetic field, in combination with specific experimental conditions, caused Lazarus superconductivity to occur more than once. “These are probably different – quantum mechanically different – from other superconductors that we know about,” said Mr Butch. “Sufficiently different, I think, to expect it will take a while to figure out what’s going on.” With its novel physics, uranium ditelluride shows every sign of being a topological superconductor, as are other spin-triplet superconductors. Mr Butch added that its topological properties suggest it could be a particularly accurate and robust component in the quantum computers of the future. Making history? “The discovery of this Lazarus superconductivity at record-high fields is likely to be among the most important discoveries to emerge from this lab in its 25-year history,” said Greg Boebinger, director of NHMFL. An attempt by state attorneys general to scupper T-Mobile US Inc’s $26 billion merger with Sprint Corp lost an ally in mid-October, when the state of Colorado abandoned the fight. Colorado made a deal with T-Mobile and Dish Network Corp, which is buying assets divested from the merger, whereby Dish pledged to bring 2,000 jobs to the state and T-Mobile pledged to deploy the next generation of wireless 5G across much of Colorado. Colorado’s decision closely followed Mississippi’s announcement that it would withdraw its opposition. Washington DC, New York, California and 13 other states were prepared to fight the companies when the trial began in early December, with 13 states (including Colorado) ready to support the merger. The two companies have agreed to divest Sprint’s prepaid businesses to Dish, and provide access to 20,000 cell sites Telecoms Opposition to T-Mobile and Sprint merger loses an ally

Research

Material displays “weird” physics but with superconductivity potential

Once dismissed by physicists for its “lack of interesting properties”, the material uranium ditelluride has attracted the attention of a team of researchers from the University of Maryland (UMD), the US National Institute of Standards and Technology (NIST), the US National High Magnetic Field Laboratory (NHMFL) and the University of Oxford in the UK. Two studies, published in rapid succession, detailed the team’s findings, and their implications for future research and development. The team’s paper in Nature Physics reported “re-entrant superconductivity” in uranium ditelluride, a discovery that furthers the case for uranium ditelluride as a promising material for use in quantum computers. Sometimes referred to as Lazarus superconductivity, the phenomenon occurs when a superconducting state arises, breaks down, and then re-emerges in a material following a change in a specific parameter – in this case, the application of a very strong magnetic field. “This is a very recently discovered superconductor with a host of other unconventional behaviour, so it’s already weird,” said Nicholas Butch, an adjunct assistant professor of physics at UMD and a physicist at the NIST Center for Neutron Research. “[Lazarus superconductivity] almost certainly has something to do with the novelty of the material. There’s something different going on in there.” Previous research, published in Science , described finding a rare and exotic ground state known as spin-triplet superconductivity in uranium ditelluride. The discovery offered the first suggestion that uranium ditelluride’s physical properties warranted investigation. “This is...a remarkable material, and it’s keeping us very busy,” said Johnpierre Paglione, a professor of physics at UMD and a co-author of the paper. “Uranium ditelluride may very well become the ‘textbook’ spin-triplet superconductor that people have been seeking... It could be the next strontium ruthenate – another proposed spin-triplet superconductor that has been studied for more than 25 years.” Superconductivity is a state in which electrons travel through a material with perfect efficiency. Compare this with copper – in conductivity, second only to silver – which loses around 20 per cent of power when transmitting over long distances.

Image: www.bigstockphoto.com Photographer Adrian Grosu

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January 2020