Engineers at Caltech have been able to observe an unusual phenomenon that may shed new light on superconductivity, thanks to the ability to turn superconductivity off and on with a flip of a switch.
The research was published in the journal Nature.
A form of carbon consisting of a single layer of atoms in a honeycomb-like lattice pattern, called magic-angle twisted graphene, is made from two or three sheets of the same form of carbon. Depending on how many electrons are added, the trilayer can be made into a superconductor or an insturment.
electrons can flow freely through materials without resistance, meaning that electricity can flow through them without any loss of heat. There are endless potential applications in the fields of computers, electronics, and other things.
In most materials, it takes place at very low temperatures, usually only a few degrees above absolute zero. electrons form pairs that behave in a fundamentally different way compared to individual electrons and condense into a quantum mechanical state that allow for electron pairs to flow without being scattered
Scientists don't fully understand the mechanisms behind electron-pair formation for some materials despite the fact that superconductivity was first discovered more than a century ago. The attraction between electrons that leads to the formation of electron pairs is due to the interaction of the electrons with the crystal lattice. The behavior of these materials is described using the Bardeen–Cooper–Schrieffer (BCS) theory, which was developed by John Bardeen, Leon Cooper, and John Robert Schrieffer.
While studying magic-angle twisted trilayers of Graphene, Nadj-Perge and his colleagues discovered that superconductivity in this material exhibits several very unusual properties that can't be described using BSC theory.
As the electrons are removed from the trilayer, they measured the evolution of the gap. The superconductivity gap is a property that shows how hard it is to add electrons to a superconductor. A certain amount of energy is needed to break the pairs. There is a difference in the amount of energy for pairs moving in different directions. The shape of the "gap" is determined by the likelihood that pairs will break.
"While superconductors have been around for a long time, a remarkably new feature in twisted graphene bilayers and trilayers is that superconductivity in these materials can be turned on simply through the application of a voltage on a nearby electrodes," says Nadj-Perge, Extra electrons are added or removed by an electric field. This allowed us to explore superconductivity in ways that can't be done in other materials.
There are two different superconductivity regimes in twisted trilayers. The presence of two regimes shows that an additional transition is likely to occur within the superconducting phase. The unconventional nature of superconductivity in the trilayers can be seen in this observation and measurement.
New insights by Nadj-Perge's team give important clues for the future theories of superconductivity. It appears that more layers make superconductivity more robust while remaining highly tunable, a property that opens up various possibilities to use twisted trilayers for superconducting devices that may someday be used in quantum science.
Adding an extra layer of Graphene made it easier to study superconductivity. This is what led to our findings.
There is evidence of unconventional superconductivity in twisted trilayer graphene.
More information: Hyunjin Kim et al, Evidence for unconventional superconductivity in twisted trilayer graphene, Nature (2022). DOI: 10.1038/s41586-022-04715-z Journal information: Nature
All Rights Reserved © 2024
