For a long time now, modern physicists’ goal has been to unlock the power of superconductivity where electricity flows with zero resistance at room temperature. While the progress in the field has been pretty slow despite the enthusiasm, a team of researchers from the University of Maryland has identified a brand new type of superconductivity.
Although electricity seems to flow instantly through the wires, electricity is carried by electrons which loses some of the energy as they bump into atoms along the way. As a result, electricity grids lose up to 7 percent of their electricity. But, when some of the materials are cooled down, the electrons pair up and begin to flow orderly without resistance. This phenomenon is known as superconductivity and it has potential to revolutionize our world as it will make electronics more efficient.
So far, we have found the phenomenon in man materials as the technology is already used to create the strong magnetic fields in MRI machines and maglev trains. However, the current implementation is pretty expensive as it requires costly equipment to keep the superconductors cold enough to continue function properly.
Interestingly, the research team from UMD has observed a new type of superconductivity which relies on highly unusual electron interactions. For instance, the electron interactions in superconductors are dictated by a quantum property known as spin. In ordinary superconductor, electrons carry a spin of ½ pair up and flow uninhibited with the help of vibrations in the atomic structure. However, in the new research, the team found evidences of a new type of superconductivity in the material known as YPtBi as the electrons have a spin of 3/2.
“No one had really thought that this was possible in solid materials,” explains Johnpierre Paglione, a UMD physics professor and senior author on the study. “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.”
YPtBi’s discovery itself was a big surprise couple of years earlier as the material doesn’t fit into main criteria. According to the conventional theory, YPtBi would need about a thousand times more mobile electrons in order to become superconducting at temperatures below 0.8 Kelvin. However, when the researchers at the time cooled the material down, they saw superconductivity happening anyway.
In order to find out the cause of the phenomenon, the researchers from UMD looked at the way the material interacted with magnetic fields. Generally, as a material undergoes the transition to a superconductor, it will try to expel any added magnetic field from its surface – but a magnetic field can still enter near, before quickly decaying away. How far they penetrate depends on the nature of the electron pairing happening within.
However, the team found that as the material warmed up from absolute zero, the amount that a magnetic field could penetrate the material increased linearly instead of exponentially, which is what is normally seen with superconductors. After a series of calculations, the researchers concluded that the best explanation for the unusual behavior was that the electrons must have been disguised as particles with higher spin which wasn’t even considered as a possibility for superconductor before.
The latest discovery of this high spin superconductor has given a new direction for the research field. Talking about the latest discovery, Hyunsoo Kim, lead author and a UMD assistant research scientist, said, “We used to be confined to pairing with spin one-half particles. But if we start considering higher spin, then the landscape of this superconducting research expands and just gets more interesting.”
While it is pretty early to conclude anything, the fact that we have a brand new type of superconductivity to test and measure adds a significant breakthrough to the 100 years of research in the field.
Paglione adds, “When you have this high-spin pairing, what’s the glue that holds these pairs together? There are some ideas of what might be happening, but fundamental questions remain-which makes it even more fascinating.”