Physicists discover entirely new quantum states as graphene meets

The graphene of “wonderful marvelous material,” which has a super thin character, has been shaking science for years with its incredible properties, but things become very interesting when you accumulate this 2D nanomaterial against itself .

In the new experiments, American physicists have found that when the graphene is coupled in a vertical double-layer stack – with two adjacent sheets of the material that almost touches – proximity produces quantum states that are not & # 39; have observed before

These recently measured states, resulting from the complex interactions of electrons between the two layers of graphene, are examples of what is called fractional quantum Hall effect – and it is only the last example of how physical science becomes strange when the materials they only occupy two dimensions.

“The findings show that stacking of 2D materials in close proximity generates a totally new physics,” says Jia Li’s physicist at Brown University.

“In terms of material engineering, this paper shows that these layered systems could be feasible in the creation of new types of electronic devices that take advantage of these new quantum room states.”

The roots of the new discovery go back some 140 years, when scientists first discovered what is known as the Hall effect: the way tension can be diverted by the presence of a magnetic field.

This so-called Hall tension operates in the transverse direction as a result of the Hall effect, which is amplified if the magnetic field being applied becomes stronger.

About a century later, physicists observed a related phenomenon, the Hall quantum effect, which is seen in two-dimensional electron systems – including recently developed 2D nanomaterials, such as graphene.

In the quantum version of the effect, it was seen that the way in which the Hall effect was amplified due to the stronger magnetic fields was not a smooth and smooth increase: on the other hand, Hall conductivity was quantified: jumping to new fixed plateaus, such as a ladder.

Later experiments revealed that some of these phenomena could be explained by fractional numbers: the aforementioned Fractional quantum Hall (FQHE) effect. Li’s team has already observed new types of FQHE in their study.

“Once again, the incredible versatility of graphene has allowed us to push the boundaries of device structures beyond what was possible,” says one of the teams, Cory Dean physicist at Columbia University.

“The precision and the ability to adjust with these devices now allows us to explore a whole area of ​​physics that was recently thought to be totally inaccessible.”

In the new work, the two layers of graphene were separated by a thin layer of hexagonal boron nitride, which was inserted to act as an insulating barrier. The device was also surrounded by hexagonal boron nitride and connected to graphite electrodes.

By subjecting this set to extremely strong magnetic fields – millions of times stronger than the terrestrial magnetic field – the team observed the FQHE states never seen in the way of interacting the electrons between the graphene layers.

Although these interesting states are new to science, it seems that they largely agree with our existing understanding of quasi-particles called compound fermions, a quantified phenomenon discovered for the first time in the FQHE investigation.

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