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Physicists discover entirely new quantum states when the graphene occurs



Graffen from a super slim "miracle material" has been shaking science for years with its incredible properties, but things are really interesting when you are stacking this 2D nanomaterial against yourself.

In the new experiments, physicists in the United States have discovered that when the graphene is assembled into a double-layer vertical stack, with two adjacent sheets of material almost touching, proximity produces quantum states that have not been observed before

new measured states resulting from complex interactions of electrons between the two graffen layers are examples of what is called the fractional quantum effect of Hall – and this is just the last example of how physical science becomes strange when the materials occupy only two

"The results show that the arrangement of 2D materials together in the immediate vicinity generates entirely new physics," says physicist Ji Li of the University of Brown.

"With regard to engineering materials, this work shows that these layered systems can be viable in creating new types of electronic devices that take advantage of these new quantum-state states."

The roots of the new discovery follow about 1

40 years ago, when scientists discovered what became known as Hall's effect: the way in which voltage can be diverted from the presence of a magnetic field.

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

About a century later, physicists watched a connected phenomenon, Hall's quantum effect seen in two-dimensional electronic systems – including more developed 2D nanomaterials, like graphene.

In the quantum version of the effect, the way the Hall effect is amplified by stronger magnetic fields is not a smooth, linear increase: instead, Hall's conductivity is quantum – jumping to new, fixed plates , similar to a staircase.

Experiments have shown that some of these phenomena can be explained by fractional numbers – the aforementioned Hall Quantum Quantum Effect (FQHE). Li's team now looks at new types of FQHE in their study.

"Once again the incredible versatility of graphene allowed us to push the boundaries of the device structures beyond what was possible earlier," says one of the team, physicist Cory Dean. from Columbia University.

"The accuracy and variability with which we can make these devices now allows us to explore a whole field of physics that has just been considered completely inaccessible."

In the new work, two graphene layers are separated by a thin layer of hexagonal boron nitride, which is placed to act as an insulating barrier. The device is also surrounded by hexagonal boron nitride and is connected to graphite electrodes. By exposing this system to extremely powerful magnetic fields – millions of times stronger than the Earth's magnetic field – the team never observed FQHE's ever-seen states in the way electrons interact between the graphite layers. new to science, they seem to largely meet our existing understanding of quasi-particles called composite farms – a quantum phenomenon first discovered in the FQHE study.

The new findings show that there may be more to these composite farms (CFs). "Besides interlayer composite farms, we also observed other characteristics that can not be explained in the composite farm model," says physicist Qianhui Shi of Columbia University. "A closer study revealed that, to our surprise, these new conditions are the result of pairing between composite farms."

While there is still a lot of research to be done before we understand All the consequences, the team says that they "interpret these conditions to be derived from the interactions of the residual pairs between CFs representing a new type of associated basal condition that is unique to Graf's two-layer structures and not described by the conventional CF model."

In other words, a graffiti layer is good, but two are out of this world.

The results are reported in Nature Physics .


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