Twisted graphene discovered a rare form of magnetism

This unique material was discovered 15 years ago, and during this time, scientists around the world have been experimenting and looking for new properties. In this article, I will talk about new research that has led to the discovery of a unique form of magnetism in graphene. So let's get started.

New properties of twisted graphene

For reference. Graphene is a sheet of carbon that is only one atom thick and has a hexagonal atomic lattice. This material has excellent thermal and electrical properties and the potential of the material is not fully revealed.

The next unique properties of graphene were discovered by a scientific group consisting of employees of Columbia University and Washington University.

In the course of numerous experiments, it was found that various exotic electronic states, including a rare form of magnetism, can appear in the three-layer structure of graphene.

The experiment was inspired by recent studies of twisted monolayers and twisted graphene bilayers, realized from two or four full sheets.

Engineers wondered what the material properties would be if graphene monolayers and bilayers were combined into a curved three-layer system.

Experimental progress and surprising results

During the experiment, the engineers folded a single-layer graphene sheet onto a two-layer sheet and twisted the sheets one degree.

After that, the resulting structure was cooled to a temperature a couple of degrees above absolute zero and began to observe.

So it was found that in this state, the structure behaved like a classic insulator. But the original state changed immediately after the electromagnetic field was applied to it.

So, when the magnetic field was directed at a sheet of single-layer graphene, the system acquired the properties of a twisted two-layer graphene. And when the direction of the magnetic field was changed, and was directed towards the two-layer graphene sheet, it began to demonstrate the properties of a four-layer structure.

It was also found that in this state the structure demonstrates unique magnetic properties.

As you know, in classical magnets, the "spin" of electrons is responsible for the magnetic properties. But in the three-layer structure of graphene, magnetism was formed due to the collective rotational motion of electrons.

The exact same structure of magnetism was discovered by another scientific group. Only such properties were observed on graphene sheets located on boron nitride crystals.

And current scientific work has shown that the same properties are observed in a much simpler design, consisting only of graphene.

As scientists emphasize, carbon is not a magnetic material and therefore it is surprising that this property can be obtained only by correctly positioning graphene sheets at the desired twisting angle.

At the moment, scientists are continuing active experiments in order to better understand the fundamental properties of new states. So scientists are only at the very beginning of studying the amazing properties of graphene.

Scientists shared the results of the experiment on the pages of the journal Nature Physics.

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