Saturday, August 13, 2016

Graphene Degrees Of Freedom

Quantum Spin

PseudospinThe list of extraordinary properties of graphene just keep on growing longer, writes: “Combining graphene with other materials, which individually have excellent characteristics complimentary to the extraordinary properties of graphene, has resulted in exciting scientific developments and could produce applications as yet beyond our imagination.”
Photo Credit: University of Manchester

An article in the form of a press release, by the University of Manchester, announces another new possibility, adding to the already-long list of possibilities that graphene holds in its promise as a super-material. This includes one of the most unusual, and also least understood, properties of this material: the additional degree of freedom that the electrons have:
It is called the pseudospin and it determines the probability to find electrons on neighbouring carbon atoms. The possibility to control this degree of freedom would allow for new types of experiments, but potentially also enable to use it for electronic applications.
Now, writing in Science, Manchester physicists demonstrate how electrons with well-controlled pseudospin can be injected into graphene. The scientists used two layers of graphene, rotated by a small angle with respect to each other and separated by a thin layer of boron nitride, another two-dimensional material and an excellent insulator. Applying strong magnetic field parallel to the graphene layers, the pseudospin state of the tunnelling electrons can be chosen.
Graphene, a slippery two-dimensional material—essentially a thin layer of pure carbon—was first discovered at this university, to wide scientific acclaim, in 2004. Having a thickness of one atom, it is the world’s thinnest known material. It is supposed to display great strength, conductivity, flexibility and transparency. If even half of such claims eventually prove true, it will no doubt be beneficial for a number of materiel science and engineering uses. The article notes that its least understood property—to wit, pseudospin—might prove its greatest benefit. We shall see.

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