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Graphene Can Host Exotic New Quantum Electronic States at Its Edges


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On a piece of graphene in a strong magnetic field, electrons can move only along the edges, and are blocked from moving in the interior.

On a piece of graphene (the horizontal surface with a hexagonal pattern of carbon atoms), in a strong magnetic field, electrons can move only along the edges, and are blocked from moving in the interior. In addition, only electrons with one direction of spin can move in only one direction along the edges (indicated by the blue arrows), while electrons with the opposite spin are blocked (as shown by the red arrows).

Credit: Massachussetts Institute of Technology

Massachusetts Institute of Technology (MIT) researchers have found additional potential for graphene by uncovering unexpected features that appear under extreme conditions and could render the material suitable for exotic uses such as quantum computing.

The researchers placed graphene under an extremely powerful magnetic field and extremely low temperature, and found that the material can effectively filter electrons according to the direction of their spin.

The segregation of electrons according to spin is "a normal feature of topological insulators, but graphene is not normally a topological insulator," says MIT researcher Andrea Young.

In addition, by varying the magnetic field, the researchers can turn the edge states on and off, which means they can make circuits and transistors.

Their research is the first time such spin-selective behavior has been demonstrated in a single sheet of graphene, and also the first time anyone has demonstrated the ability to transition between these two regimes, according to MIT professor Pablo Jarillo-Herrero. The research represents a new direction in topological insulators.

"We don't really know what it might lead to, but it opens our thinking about the kind of electrical devices we can make," Young says.

From MIT News
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