Researchers have observed an exotic type of superconductivity that relies on highly unusual electron interactions, which may open the door to novel types of research in the future.
The behavior, regarded as elusive, has not been seen before. A study describing the findings has been published in Science Advances.
"No one had really thought that this was possible in solid materials," said senior author Johnpierre Paglione, from the University of Maryland, in a statement.
To understand what’s going on, we first need to get to grips with superconductivity itself. It refers to a process through which materials can conduct electricity with no resistance, meaning they don’t give off any heat or energy. It often relies on temperatures approaching absolute zero (0 Kelvin, or -273.15°C).
In superconductors, the electrons are dictated by something called spin, which is a quantum property relating to the angular momentum of the electrons. Usually, they carry a spin of 1/2, but in this research, the team found particles with a spin of 3/2 in a material called YPtBi. This, they say, is a new type of superconductivity.
"High-spin states in individual atoms are possible but once you put the atoms together in a solid, these states usually break apart and you end up with spin one-half," said Paglione.
What’s particularly unusual here is that YPtBi is not a very good conductor, which is usually a requirement of superconductors. So when it became superconducting at a higher temperature than thought, 0.8 Kelvin (-272.35°C), the scientists noted something interesting was going on.
By studying the interaction of the material with a magnetic field, the team were able to work out the nature of the electron pairing in the superconductor. By carrying the temperature and applying a small magnetic field, the team found that the electrons were disguised as particles with a higher spin.
"We used to be confined to pairing with spin one-half particles," said lead author Hyunsoo Kim from the University of Maryland. "But if we start considering higher spin, then the landscape of this superconducting research expands and just gets more interesting."
The team now want to try and work out how the electron pairs are being held together inside this superconductor. They note that the unconventional pairing could represent a novel form of superconductivity that could lead to the development of a new range of superconductors.