A team of researchers from Cornell University has now identified a possible third type of superconductor, a g-wave superconductor.
Until now, we basically had two types of superconductors namely s-wave and d-wave superconductors. Researchers had theorized the presence of other types of superconductors long ago and this new research has identified a new type for the first time.
This groundbreaking research recently appeared in Nature Physics. The lead author of the paper is doctoral student Sayak Ghosh.
What is a superconductor?
A superconductor is a substance that conducts electricity without any resistance meaning electricity can flow with 100% efficiency. The problem is the materials need ultra-low temperatures to exhibit actual superconductivity.
Almost all superconductors are made up of Cooper pairs of electrons that combine a spin-up electron with a spin-down electron, removing the material’s electrical resistance along the way
Until now, only two types of superconductivity fits this description, s-wave, and d-wave.
What is an s-wave superconductor?
In s-wave, the cooper pairs point directly to each other. So, its net angular momentum is zero.
What is a d-wave superconductor?
In d-wave, there is a positive angular momentum along one axis and negative along a second axis. So, here the cooper pairs have two quanta of angular momentum.
Physicists have theorized the existence of a third type of superconductor between these two so-called “singlet” states: a p-wave superconductor, with one quanta of angular momentum and the electrons pairing with parallel rather than antiparallel spins. This spin-triplet superconductor would be a major breakthrough for quantum computing because it can be used to create Majorana fermions, a unique particle that is its own antiparticle.
Strontium ruthenate has been a leading candidate for p-wave superconductor.
Thus the team set out to find whether strontium ruthenate is a highly desired p-wave superconductor. But a super-detailed resonant ultrasound spectroscopy of Strontium ruthenate shocked them. They found a completely new kind of superconductor – the g-wave.
This g-wave superconductor was found to have angular momentum of four. No one has ever even thought that there would be a g-wave superconductor.
“This experiment really shows the possibility of this new type of superconductor that we had never thought about before,” says physicist Brad Ramshaw, from Cornell University. “It really opens up the space of possibilities for what a superconductor can be and how it can manifest itself.”
“If we’re ever going to get a handle on controlling superconductors and using them in technology with the kind of fine-tuned control we have with semiconductors, we really want to know how they work and what varieties and flavours they come in.” the researcher added.
In the future, the team will be looking for the elusive p-wave superconductor. They will be studying Strontium ruthenate further as well. Hopefully, we will be able to get superconductors working at warmer temperatures soon.
Sayak Ghosh, Arkady Shekhter, F. Jerzembeck, N. Kikugawa, Dmitry A. Sokolov, Manuel Brando, A. P. Mackenzie, Clifford W. Hicks, B. J. Ramshaw. Thermodynamic evidence for a two-component superconducting order parameter in Sr2RuO4. Nature Physics, 2020; DOI: 10.1038/s41567-020-1032-4
Press Release: Cornell University