Ensslin’s team at the Swiss Federal Institute of Technology Zurich (ETH) has created the first superconducting quantum interference device using graphene to demonstrate the interference of superconducting quasiparticles. This significantly extends the range of uses for carbon graphene.
The paper has been published in Nature Nanotechnology, DOI: 10.1038/s41565-022-01222-0. This research is expected to contribute to the development of quantum technology and opens up new possibilities for superconductivity research.
In 2004, Konstantin Novoselov and Andre Geim created the first two-dimensional crystal consisting of only one layer of carbon atoms. This material was named graphene and has since attracted a great deal of attention and development. Graphene is the thinnest and strongest new nanomaterial with the best electrical and thermal conductivity known to date. As research continues, more properties have emerged.
Now, for the first time, ETH researchers have prepared superconducting elements, known as SQUIDs (Superconducting Quantum Interference Devices), from bilayer twisted graphene for demonstrating superconducting quasiparticle interference. In quantum technology, these sensitive sensors are used as quantum bits (qubits). These fundamental elements can be used to perform quantum operations and to build more complex circuits.
According to the official press release, the results were first built on the work of Klaus Ensslin and Thomas Ihn’s team at the ETH Solid State Physics Laboratory, it had demonstrated about a year ago that twisted bilayer graphene could be used to make the Josephson junction, a fundamental component of superconducting devices.
However, the researchers were not satisfied with their breakthrough, because these graphene SQUIDs also have little advantage over traditional aluminum SQUIDs, and like traditional SQUIDs, it must also be cooled to near absolute zero (2 degrees above absolute zero).
According to Enslin, they clearly expand the range of applications: “Five years ago, we were able to show that graphene could be used to make single-electron transistors. Now we’ve added superconductivity to the mix.”
Depending on the applied voltage, graphene can change between insulating, conducting, and superconducting states. In addition, this result now shows that we can combine transistors and superconductors from semiconductors in a single material to make a new type of SQUID.
In quantum technology, SQUIDs can hold quantum bits and therefore can be used as components to perform quantum operations,” Enslin noted. In addition, typically, transistors are made of silicon and SQUIDs are made of aluminum, and different materials require different processing techniques, but now they can both be made of graphene.”
According to Ensslin, their future research will focus on using graphene on the same crystal to combine the advantages of both quantum systems.
Ensslin added that there are different superconducting phases within graphene, but there is not yet a theoretical model to explain them. The latest results will also open up new possibilities for superconductivity research, and with these components, it may be possible to better understand how superconductivity arises in graphene.
