A new quantum component made from graphene

The first two-dimensional crystals consisted of just one layer of carbon atoms. Since then, this material has been used in many things.

Graphene is used to reinforce products such as tennis rackets or car tires. It's an interesting subject for fundamental research as physicists discover new, amazing phenomena that have not been observed in other materials.

The correct way to twist it.

Bilayer graphene crystals, in which the two atomic layers are slightly different, are of interest to researchers. One year ago, a team of researchers led by Klaus Ensslin and Thomas Ihn were able to demonstrate that twisted graphene could be used to make Josephson junctions.

Researchers were able to make the first superconducting quantum interference device, or SQUID, from twisted graphene because of this work. In medicine, geology and archaeology, conventional SQUIDs are being used. Even the smallest changes in magnetic fields can be measured. SQUIDs require cooling with liquid helium or nitrogen when in use.

The elements for carrying out quantum operations can be found in SQUIDs. "SQUIDs are the building blocks of more complex circuits," Ensslin says.

The spectrum is getting bigger.

The SQUIDs created by Elas Portolés are not more sensitive than those made from aluminum and have to be cooled down to temperatures below absolute zero. It isn't a breakthrough for SQUID technology. It broadens the application spectrum considerably. Five years ago, we showed that single-electron transistors could be built using Graphene. "Now we have added superconductivity."

There is a way to control the behavior of the Graphene by biasing it. The material can be either conducting or insulated. There are a lot of opportunities offered by solid-state physics.

The two fundamental building blocks of a Semiconductor and a Superconductor can now be combined in one material. It is possible to make novel control operations. The transistor is usually made from aluminum and Silicon. Different processing technologies are required to process these materials.

The production process is very difficult.

Five years ago, an MIT research group found superconductivity in Graphene, yet there are only a dozen or so experimental groups that look at this phenomenon. Only a small number of people are capable of converting a piece of metal into something that works.

The challenge is that scientists have to carry out several delicate work steps one after the other: first, they have to align the graphene sheets at the exact right angle relative to each other The next step is connecting the holes. The twist angle would disappear if the graphene were to be heated up. This is an extremely challenging job because the standard chip technology has to be adjusted.

The idea of a hybrid system.

Ensslin is thinking about the future. There are a lot of different qubit technologies that are being assessed. Various research groups within the National Center of Competence in Quantum Science and Technology are doing this most of the time. It could be possible to combine the benefits of the two systems if they are combined. There would be two different quantum systems on the same crystal.

New possibilities for research on superconductivity are generated by this. We might be better able to understand how superconductivity in Graphene comes about with the help of these components. We don't have a theoretical model to explain the phases of superconductivity in this material.

The study is in a journal.

There is more information about Elas Portolés et al. There is a DOI titled " 10.1038/s41565-022-012".

Journal information: Nature Nanotechnology